The state-run Institute of Meteorology and Water Management (IMGW) issued its predictions on Wednesday, Polish state news agency PAP reported.
IMGW spokesman Grzegorz Walijewski said the heatwave would continue through the end of this week, with more "tropical nights” for Poland.
At the same time, the country will be hit by torrential rain, rainstorms accompanied by winds of up to 75 kilometres per hour, and possibly hailstorms, starting in the early hours of Thursday, he warned.
The official said Poland had witnessed its hottest temperature of the year on Tuesday, with 35.7 degrees Celsius recorded in the city of Ostrołęka, in the country's central Mazowieckie region.
Poland was also Europe’s hottest country on Tuesday, alongside Spain, he added.
On Wednesday, the highest temperature, 34.7 C, was recorded in Pułtusk, a town 70 km north of Warsaw, according to the IMGW.
Meanwhile, the state weather institute has issued rainstorm alerts for Poland’s western and southern regions for Thursday, the PAP news agency reported.
First-degree rainstorm alerts have been issued for the western Lubuskie and Wielkopolskie provinces, for the Dolnośląskie and Opolskie regions in the southwest, and for parts of the southern Śląskie province.
A second-degree rainstorm alert was in place for parts of the Dolnosląskie region, which could see rainfall of up to 45 mm, the IMGW said.
(pm/gs)
Source: PAP, IMGW