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).
