August 2026 heatwave diary

As I was saving for posterity the record-breaking heatwave which hit central Europe in late June 2026, I sadly got it right it would not be the only one this summer. In Poland it was the second heatwave this summer, in most parts of Europe - fourth. And the fifth one is in the offing in France and in the UK.

Thursday, 16 July 2026
I get external roller shutters installed outside my windows facing north-east. Glad I hadn't put it back until next summer season, as they will prove to serve as a brilliant shield from heat.

Thursday, 30 July 2026
This heatwave commences on Thursday too, with a lovely pre-dawn low of +15C. Before the onset of high temperature I managed to cool the dwelling down to +21C, which is a decent result, given walls have accumulated a lot of heat. Afternoon high of +31C is still tolerable, especially with wind gusts up to 30 km/h.

Friday, 31 July 2026
The night wasn't that lovely, since temperature did not drop below +20C, actually with a low of exactly +20.0C it ranked as a tropical night, a fifth one this year (nine tropical nights were endured in Warsaw in summer 2019, the record is likely to be broken this year).
The afternoon high of +33C was markedly lower than forecasts of +36C. Moderate cloud cover has not let the air warm up. Nevertheless, it does not feel nice. I return home after a beer or three in town around 10 p.m. and the air remains sultry, yet Ursynów is noticeably less warm than the city centre.

Saturday, 1 August 2026
A short, intense downpour hit Warsaw overnight. Cloud cover did not let the heat get released into the skies. Consequently, night-time low reached +21.3C (sixth tropical night this summer). Air in the morning is horridly humid. In the afternoon temperature climbs to +31C, with heat index even higher (air humidity > 50%). After 3:00 p.m. a thunderstorm hits Warsaw. It does not bring the temperature much down, but air humidity is even higher. Two next showers in the evening.

Sunday, 2 August 2026
Finally a cooler morning with a low of +17C, but air humidity close to 100%. The entire day brings some relief from the heat, as temperature does not rise above +25C, giving some time to brace for the second blow of this heatwave.

My eyes in the meantime are on Hungary. The country's core nuclear power plant, Paks, is running below its full capacity due to low level of Danube and consequent deficiency of water to cool the bloc. A full shutdown seems inevitable. Hungary is in the focal point of the current heatwave. Temperatures in Budapest reached daytime highs in excess of +35C each day since 30 July. The climax of the scorching episode is forecast for 5 August, with high above +40C and low of +24C. The country faces a threat of paralysis amid a deadly heat. Emergency situation is also in neighbouring Romania, where power plant's cooling unit is brought to a halt by deficiency of water. Since grids in the region are interconnected, several countries, including Poland may face power outages. In Poland such incidences have not taken place since August 2015.

Monday, 3 August 2026
The night and early morning were supposed to be brisk. In fact, with accursed cloud cover, temperature did not drop below +18C with high air humidity. During the working week Warsaw will need to endure at least one day-time high above +35C. Today, as clouds did not fade during the day, temperature reached only +29.5C. In the afternoon it felt astonishingly comfortable, as the wind took the gloss of the heat. After sunset an electrical thunderstorm with moderate rainfall comes over Warsaw.

During the last harsh winter I began counting down days until March (when snow and frost were likely to ease off). Time to start counting down days until September, when at least tropical nights are unlikely.

Tuesday, 4 August 2026
One more night-time rain has passed over the capital. With a low of +19.9C the night does not formally rank as tropical, but given air humidity close to 90%, the morning is anything, but enjoyable. During the day temperature rises to +31C, however with air humidity near 50%. Sultry. In southern Poland day-time highs reach +37C.

The grids in Hungary and Romania have not yet collapsed, as large industrial off-takers have cut down on or halted manufacturing. With effects of drought being felt for weeks to come, the energy-saving measures will remain in place after the heatwave peters out.

Wednesday, 5 August 2026
The night was a bloody hell. With clouds in place, temperature did not decline below +22C (seventh tropical night this year). Past 7:00 it was already +24C and vapour was hanging in the air. Warnings of record-breaking heat have not materialised in Warsaw. Day-time high of +35.7C is over one Celsius degree short of Poland's capital August all-time high (+37.0C on 8 August 2013). But in Kozienice, less than 100 km south of Warsaw, temperature climbs to +38.8C. Many spots in southern Poland today broke their records of maximum temperature, yet the fresh (38 days old) countrywide heat record remains untouched.
Inside: +25C, but with air humidity of 70%, already uncomfortable.

In Austria and Slovakia temperatures rose above +41C for the first time in history.

The Paks nuclear power plant in Hungary is shut down. Grids in several countries south of Poland, i.e. Hungary, Romania and Moldova are under pressure. Blackouts are averted thanks to decreased demand from large manufacturing plants. Economic growth has led to the global warming. Now the global warming tapers the economic growth.

Thursday, 6 August
The eight tropical night this summer. The worst part of the morning is wearing a suit and getting with a suitcase and a bag to a car parked outside (+24C and sultry air at that moment). I set off from home for a two-day business trip, firstly to Podlasie, then directly from there, to Podhale. The entire trip, 1,300 kilometres, taken by car (hybrid Toyotas do not emit little CO2 in motorway driving), thus feeling guilty of contributing to the hell which we are enduring.
Forecasts of cold front bringing abundant rainfall and relief from the heat in the early afternoon in Warsaw have not materialised. In Podlasie temperature reached +35C (according to car thermometer, but in line with official readings). After a meeting with a client I stopped by at a petrol station to swap suit for shorts and t-shirt. On my way to Kraków I encountered small hail. I stopped over for a much-belated lunch somewhere beyond Grójec and temperature out there was (according to car thermometer) +37C. Somewhere close to Kielce the highest reading was +39C. Aircon in the car did its job well, but in a KFC restaurant despite aircon running at full blast, it kept the interior at some +25C. Efficiency of aircon in my hotel room seems insufficient.

Friday, 7 August 2026
The aircon in my hotel room produced more noise than cold air overnight. Kraków needs to get through a tropical night, during which I switched off the aircon fuse and opened the window. In Warsaw morning rainfall sends temperature below gently +20C. Markedly below +30C during the day. Some proper relief from the heat due over the weekend.
So far there have been 16 hot (maximum temperature above +30C) days this year in the capital of Poland (vs. record-high number of 24 in 2015 and 2024), but the summer has not run out. Tomorrow’s high is forecast to be above +30C, but it will be a one-day incidence of heat. Counting down days until autumn...

June 2026 heatwave diary

At first I wanted to call it a "2026 heatwave"  but how can I assure in early July it will be the only such intense and abnormal hot spell this summer?

Tuesday, 16 June 2026
Judging by average temperature for the first half of the month, so far this is the coolest June since 2014. with hindsight, it turned out to be over 2 Celsius degrees warmer than 1991-2020 average in Warsaw.

Saturday, 20 June 2026 – Sunday, 21 June 2026
The first two days this year with highs above +30C, the latter humid and stormy. Around that time long-term forecasts hint at serious heatwave incident. At first they seem to be a model error, but with each next update, the heat dome prediction solidifies.

Thursday, 25 June 2026
Here it begins. Night-time low of +15C means at dawn it's still pleasant and one can keep the dwelling cool. Inside: between +21C and +24C. Temperature tops at +31C, so no tragedy.

Friday, 26 June 2026
The night is not that chilly, no colder than +18C, afternoon high of "mere" +31C, which is relatively bearable vs. what lies ahead. Inside: between +22C and +24C, humidity 60%

Saturday, 27 June 2026
I return home from an open-air party around midnight. At that time temperature in Powsin on the verge of Las Kabacki stood at +21C, while at the same time in Ursynów it declined to only +24C. Urban heat island proven existent. The last night when pre-dawn temperature dropped below +19C. In the morning temperature shoots up to climb to awful +34.7C, nearing the June maximum temperature record of +35.3C set on 26 June 2019, which is bound to be broken tomorrow. A country-wide June maximum temperature record for Poland has been beaten. Weather station in Słubice reported +38.5C, vs. previous record of +38.3C set also on 26 June 2019 in Radzyń. Inside: between +20C (air humidity above 70%) and +25C (air humidity just below 60%, not nice).

Sentence to be pondered upon: "Our houses have been built for a climate which no longer exists." For decades the primary concern was how to keep the dwellings warm during the colder half of the year, while growing frequency, intensity and duration of heat waves necessitate also keeping dwellings cool when outside it's well above +30C.

Sunday, 28 June 2026
First tropical night this year, with low of +20.4C in Warsaw. In western Poland minimum temperatures measured do not drop below +25C. From early morning the temperature soars. At 9:00 it reaches +30C, at noon it climbs to +35.7C, setting a new short-lasting heat record for the capital of Poland. Late in the afternoon a country-wide record (+40.2C measured on 29 July 1921 in Prószków near Opole) is shattered. The weather station in Słubice officially reports a high of +40.5C. Warsaw's highest ever temperature of +37.0C measured on 8 August 2013 is rendered outdated with a new readout of ghastly +38.1C. Inside: between +25C (air humidity 60%) to +26C (air humidity 55%). Awful, but cool compared to the oven outdoors.

The sentence to be pondered upon (continued). Air conditioning is a quick fix, lets one function properly, but has its dispersed cost. Prevalent in the US, seldom installed in private dwellings in Europe. With the current electricity output from solar panels it can be powered with nearly green energy during the day. This is the theory. In recent days around midday no more than 60% of energy output in Poland came from PV, while in the evenings demand for energy in Poland was satisfied in over 80% from conventional units, i.e. burning fossil fuels. Bear in mind AC removes the effect, not the cause. Walls give off heat after the sunset and you need to run AC overnight too to keep a dwelling cool and unless the electricity comes from a battery storage charged up during the day, you need conventional energy to power the AC. Besides, AC blows out hot air outside a cooled off building, thus increasing temperature to its neighbours and intensifying the urban heat island effect. I believe primary investments in thermal modernisations should involve proper insulation and protection from heat, not to let it trespass into a building and use of AC to augment it, when construction measures (thick insulation on walls and roofs, triple-glazed windows, external blind rollers, trees giving shade, ripping off paved urban areas) are insufficient. My take on duplicity of architects has been laid out here and I uphold it. I believe a balanced take is presented here.

Monday, 29 June 2026
With a minimum temperature of +24.7C last night was the warmest ever in Warsaw. I slept with windows closed, opened them after waking up at 4:00 a.m., to lock up the flat at 6:30 a.m. and head for air-conditioned office. Outside around 7:00 a.m. it was already +27C. To my surprise, underground stations and trains have not been warmed up horridly, I would hazard a guess it was around +25C inside. At Rondo ONZ station, despite early hour, droves of people were rushing to offices to find corporate shelters from heat. I admit it felt nice to cut off the awful heat, with today's high of +36.0C. No storms nor heavy rain have haunted Warsaw. Inside: temperature slowly increases to +27C (humidity: 60%), no longer comfortable, not yet tragic. Today administration of the building I live in issued a permission to install external blind rollers in windows of my bedroom and kitchen, both facing north-eastern side. In previous years, they were unnecessary, as the south-western living room ones did their job well enough. During the current heatwave I could swelter at 6:00 a.m. in my bedroom.

On both 28 June and 29 June daily temperature in Warsaw averaged out +30.6C, beating the previous record of +29.3C set on 8 August 2015.

Tuesday, 30 June 2026
The third tropical night in row. With temperature reaching a low of +21C it brings a minimum relief and lets the dwelling cool down a bit. Around 6:00 a.m. a short shower comes over Warsaw. It gives some little respite to the dried-up soil and leaves the air humid. Afterwards the heat is less tolerable, despite lower absolute temperature (max. +32C). Temperature creeps up above +30C around 2:00 p.m. which looks luxuriously cold. Inside: between +24C (humidity: 70%) and +27C (humidity: almost 60%).

Wednesday, 1 July 2026
The fourth tropical night in row, with low of +21C. In the morning outside it feels much better than inside, where neighbours' walls heat up mine. The afternoon is sultry, with high of +32C and much vapour in the air. Late evening brings a thunderstorm which puts the period of intense heat to a long-awaited end. Chasing away the warmth accumulated in buildings will take a while. This is formally the last day of the heatwave, with tomorrow expected to fall overnight to +17C and climb to +27C in the afternoon. Next days are about to be cold (in July terms) and I keep fingers crossed for that forecast.

The heatwave formally lasted 7 days and was not as awful as 15 days in a row with maximum temperature above +28C in August 2015. Until early July we have had so far 9 days this year with day-time highs above +30C, vs. long-term average of 9.5 days per year (1991 – 2020 benchmark period) and maximum number of such days of 24 in a year (2015 and 2024).

Finally, not an extremely warm summer (in Poland)

After a streak of six autumnal and wintery months in a row with anomalously high average temperatures (from October 2019 to March 2020 each with mean temperature no less than 2 Celsius degrees higher than 1981-2010 average) spring and summer months of 2020 bring temperatures closer to long-term averages.

April 2020 was merely 0.7C degrees warmer than long-term average, while May 2020 went down in history as the coldest since 1992. This pertains to measurements in Warsaw, since in most parts of the world the month was the hottest since records began.

June 2020 was over 2C degrees hotter than 1981-2010 average, but only 1.3C degrees warmer than 1991-2020 average which will become a benchmark in 2021. The month did not seem hot to me, as I still had in mind how scorching it was last year. Indeed, June in 2020 was 3.5C degrees colder than in 2019. In 2020, only once over the entire month the temperature exceeded +30C. In terms of rainfall, the precipitation of 166 millimetres (vs. long-term average of 70 millimetres) has brought short-term relief from the drought.

July 2020 was 0.1C degrees warmer than 1981-2010 average and 0.5C degrees colder than the 1991-2020 average, which meant the weather was clement. Sadly, it could have done with more rainfall, as only 48 millimetres have fallen on the ground, which accounts for 65% of monthly average precipitation.

Fortunately, so far we have had only 2 days with temperatures topping above +30C (12 June and 28 July), yet on both less than +31C. This, along with pleasantly cool nights and early mornings has made working from home (no aircon here) quite comfortable.

August looms as the hottest month of the year, with conceivable incidences of inflows of air masses from Sahara, those which these days bring +40C temperatures in Spain or France. I hope in Poland the onslaught of heat will be short-lasting, as sweating in front of the computer in my living room is not what I would wish on my worst enemy.

I recommend you read Michael’s post on the epidemic. Next week I will attempt to write my own note, hoping the story does not unfold tragically quickly (since in some time a tragic time is inevitable).

The hottest June, ever

May 2019 around the middle of its second decade, stood a chance of being the coldest since 1991. Eventually, thanks to lack of incidences of extreme cold (no frost, +1.1C on 6 May was the coldest moment of the previous month) and after reasonably warm third decade, the mean temperature stood at +13.5C, not much short of the long-term (1981-2010) average of +14.0C.

The first days of June brought the first whiff of proper summer, long awaited after spring deficient in warmth we had got accustomed to in previous years. Day-time highs over the first decade of the month did not reach +30C. The first incidence of heat was recorded on 11 June. The month saw in total 8 days with temperature exceeding +30C (beating the yearly norm by 60%). Over the entire month the temperature did not fall below +12C. The heat waves were interspersed with just warmth…

The hotness reached its climax on 26 day of the month when June and all-time records were broken in several weather stations across Poland. In Warsaw the official meteo station on the fringes of Okęcie airport recorded +35.3C (thus the previous record set on 21 June 2000 of +35.1C was broken). Poland-wide record of +38.0C was also broken on that day, when +38.2C was measured in Radzyń, Wielkopolska. The heat eased off the day before yesterday and yesterday. I have made use of +12.1C dawn-time low yesterday to air out and cool down the dwelling and thanks to this I have enjoyed mere +24C inside, while outside temperature soared again to +35C (precisely it topped at +35.2C)

As I write this post, full-month temperature data lack the last 5 hours, but with a sufficient dose of certainty I might say the temperature averaged out +22.9C, which makes it the hottest June since records began (well ahead of June 1917 whose mean temperature ran at +20.4C) and the third hottest month in Warsaw since records began, after July 2006 (+23.5C) and August 2015 (+23.0C).

The current decade has been abundant in incidences of record-breaking heat and near-misses in that respect in Warsaw…

29 April 2012, +30.4C, when temperature peaked above +30C for the first time in April

8 August 2013, +37.0C, all-time heat record in Warsaw

21 March 2014, +22.4C, short of +23.0C March heat record

1 September 2015, +34.9C, new September heat record set

23 December 2015, +14.4C, short of +15.0C December heat record.

2 November 2018, +19.2C, new November heat record set.

If the global warming (no matter if the mankind has caused or has just contributed to inevitable natural trend) is not halted, heat waves will be more frequent and will last longer, making our lives more miserable… The climate is akin to a pot of water. While it gets hotter it begins to swirl. The same happens to the weather. Anomalous events, such as heat waves, droughts, floods, cold snaps, blizzards will get more frequent. In terms of precipitation and temperatures we will see higher deviations from the mean, weather events will go into different extremes on different continents…

Short-term hope lies in long-term forecasts. July and August are predicted to be colder than June and near long-term average, which gives some hope for a nice warm, yet not sultry summer.

Hotter than ever, drier than ever…

Gone is probably one of the hottest summers in the history of Poland. Gone are the tiresome heatwaves. Gone is the thermal discomfort we have endured for weeks.

I am fond of statistics, in particular of weather statistics, hence I have taken the troubled to quantify August 2015 which was the warmest August in the history of temperature measurements in Warsaw - average temperature reached +23.0C, beating August 1992 when it stood at +21.5C and was the second warmest month in the history of Warsaw since 1880, after memorable July 2006, when mean temperature was +23.5C.

The chart below displays quite well the temperature anomalies witnessed last month in Warsaw. Over virtually the entire month average temperature was above mean temperature for specific days, with considerable deviations at the end of the first decade of the month and in its very last days.

 

The month had a misleadingly cool commencement. On 1 August I was setting off to the mountains on 4 a.m. and outside it was quite chilly, somewhere behind Nadarzyn car thermometer showed +5C. I thought I could do with winter tyres as well…On the same day temperature shot up and two days later exceeded +30C.

The heat wave according to the phenomenon’s pure definition lasted 11 days, since each day from 3 August 2015 to 13 August 2015 maximum temperature recorded was above +30C, and was the longest heat wave observed in Warsaw ever (oddly enough the average number of days in a year when temperature is above +30 is mere five). Had the definition been adjusted down by one Celsius degrees, the heat wave would have lasted incessantly for 15 days, until 17 August.

The heat wave reached its climax on Saturday, 8 August 2015, when temperature rose to +36.6C, 0.4C short of heat record set exactly two years earlier. The day was followed by record-hot night, when temperature did not drop below +22C even before dawn. The average temperature over 24-hour interval stood at +29.2, far warmer than in Athens, Rome or in Madrid on an average day in July.

Days between 19 August 2015 and 26 August 2015 brought blissful relief from heat, with day-time highs in mid +20Cs and lows below +15C. Had it not been for that colder period, August 2015 would have gone down as the hottest month ever.

Last days of August 2015 and 1 September 2015 brought another influx of unusual heat, with temperatures in Warsaw reaching +34.7C and +34.5C on respectively 31 August 2015 and 1 September 2015, with the latter breaking the previous heat record for September set on 7 September 2008 (+30.7C).

On top of this deficiency of precipitation also made itself felt – rain fell twice in August 2015 – on 16 August and on 25 August with the two showers being a drop in the ocean that should lash down from heavens to bring back hydrological balance in Poland.

Abnormally high temperatures have given nearly everyone a rough ride. As experts point out, it is not the intensity, but length of the heat wave that determines its tiresomeness for people. Hence three days with temperatures peaking at +37C are more bearable than two weeks of heat reaching only +32C each day.

Despite weather conditions hazardous for health, number of reported diseases caused by heat was not appallingly high, especially if cases of drowning in rivers and lakes are counted out.

Whoever could, took shelter from the heat in air-conditioned interiors. With increasing number of offices, other public buildings and flats having air-con put in and turned on, electricity consumption soared, reaching levels last observed in record-cold first decade of February 2012 (when temperatures at night dropped well below –20C). In the meantime, power-generating blocks in power plants could not be cooled properly (due to shortage of water and its too high temperature) and this resulted in planned blackouts. Several industrial off-takers faced restrictions on consumption of electricity, something that was just a matter of time and what happened for the first time since the ultimate downfall of planned economy in 1990.

Drought also closed the gates to the forests for tourists, on account of extraordinary peril of fire. And last, but no least, many trees began to shed their yellow leaves far earlier than usual. Despite the heat, it felt like autumn. Yesterday, when I cycled via Las Kabacki, paths were covered with a blanket of leaves, something which ought to be observed in late September.

The problem with the heat in Poland is that an average Pole has no chance to shield it. In winters, when temperatures reach –25C you simply stay at home, keep warm (unless your housing conditions are dire) and only the thought of the bottom line on your heating bill wipes the smile off your face. In summer, an average Pole needs to withstand temperature of +30C inside their dwelling. While in shopping malls and modern offices and in cars air-conditioning is nearly always in place (what an incentive to stay overtime), residential housing still lacks it on larger scale, but given the direction of climate changes, air-conditioning will not be just a luxury, but a must, allowing one to survive the summer comfortably. These musts, while once they grow prevalent, will boost energy consumption again… Summer electricity bills might soon become the price to pay for lower heating bills in milder winters…

And what is about to ensue thereafter? Today temperature fails to creep above +17C, it is astonishingly chilly if we bear in mind just five days ago it was +34.5C. Weather patterns do not tend to recur, therefore record-hot August might to followed by: very warm autumn or a very cold autumn, or a typical autumn, or by any combination of the three. Long-term numerical forecasts foresee an anomalously mild winter, while some signs wildlife and plants send to us indicate a harsh winter ahead.

My own tolerance for heat somewhat decreased this year. In 2012, 2013 and 2014 I actually did not mind it when temperature was above +30C. I remember well walking around the office around midday on 8 August 2013. Temperature was +36C, I was wearing suit trousers and long-sleeve shirt with pulled up sleeves and felt no specific desire to rush to the air-conditioned office. This year even in the temperature of +30C I could sit idle, have nearly nothing on and soak with sweat. There were several night when I could not sleep a wink because of the heat. Drained of energy, I began to feel sympathy with Greeks whose laziness is to some extent grounded in the climate they fail to endure.

In the meantime my holiday plans have gone down the drain :(. The travel companions, while I made the reservation and reached out for money to make a confirmatory payment, dropped off, while our destination, Hungary, was invaded by scores of ruffians (pardon the expression) and actually we would be in a quandary, wondering how the situation would unfold. While it is politically correct to take pity on refugees and sympathise with humans who had to flee their war-inflicted homelands, I argue it is advisable to ask ourselves whether not only we can afford to play host to refugees (the answer is clear), but whether those people would assimilate into our civilisation. As a nation, Poles would respect their culture, religion (unless they are lunatic Muslims attempting to wage a war against the rotten West), etc., but in return they would need to adjust to customs of the country which offers them asylum. Frankly speaking, I do not embrace a prospect of thousands of unemployed mouths to feed inhabiting refugee camps or irate hooligans vandalising public infrastructure or robbing trucks with food (as they allegedly did in Hungary), exhibiting their anger with the fact Europe fails to greet hordes of immigrants with open arms.

This may be unpopular, but the influx of migrant to Europe, stemmed or not, is the price to pay for attempting to spread democracy in areas of world where dictatorship would simply prove better. Democracy is by far the best political system, provided a society has reaches the proper level of development. Guys from the United States who excel at breaking out wars thousands of miles from their borders should also realise it.