Poland's national weather service on Wednesday issued its highest alert level for Warsaw and large parts of the country during a prolonged heatwave that has struck the country.
It predicted the most extreme conditions for the south-east, with temperatures reaching 40 degrees Celsius. The forecast high for Warsaw is 38 degrees.
"The night from Wednesday to Thursday will also be tropical, with temperatures not falling below 20°C, making it harder for the body to recover," a spokeswoman for the Institute of Meteorology and Water Management told Tok.fm radio.
Mist-spraying stations have been installed at several locations in central Warsaw.
The Polish capital has a population of 1.9 million, while the wider Warsaw metropolitan area is home to around 3 million people.
Prime Minister Donald Tusk appealed directly to businesses and employers. "Take care of your employees, your colleagues, and yourselves. If you have air conditioning, don't hesitate to use it today," he said in a video post on X.
He encouraged employers to allow staff to work from home: "And if it simply becomes too much, you should definitely take a break."
Unlike Hungary to the south, where the Paks nuclear power plant narrowly avoided a complete shutdown because of the Danube's low water level, Poland has so far experienced no problems with electricity generation. Poland has no nuclear power plants and relies primarily on its coal-fired power stations to meet peaks in electricity demand.
Meteorologists have forecast storms accompanied by heavy rain and hail for western Poland on Wednesday evening. A noticeable drop in temperatures is not expected until Friday.