A tropical night has been measured at eleven weather stations in Sweden the night before Sunday: Karlskrona, Malmö, Utklippen, Falsterbo, Skillinge, Öland's northern and southern cape, Hanö, Harby and Skurup.

-To be so late in the season you have to say that it is unusual, says Alexandra Olsson, meteorologist at SMHI.

A tropical night means the temperature does not drop below 20 degrees all night. The most recent date on which a tropical night has been measured is September 5, which was in 2002 on the North Island headland.

"There is still opportunity"

Parts of Svealand and Norrland have also had high temperatures during the night, and the heat is expected to keep up during the early Sunday.

In eastern Götaland, there may be a new heat record for September during Sunday. The current record for September is 29.1 degrees and was set in Stehag in Skåne in 1975.

"There is still opportunity, but it depends a lot on the bursts that are currently over the eastern parts of Götaland, how quickly they will move away to the Småland coast and Östergötland," says Alexandra Olsson.

Large parts are affected

The warm, humid air that is over Sweden is expected to put it in other ways. Cooler air from the west is on the way, and when they crash, thunderstorms are formed and powerful bursts that can create problems with water collections on the roads.

-We have these risks issued for the northern parts of Götaland and large parts of Svealand, even after Jämtland County and Gävleborg's inland. There are large parts of the country that will be affected by heavy rain and, perhaps, heavy thunderstorms at times, says Alexandra Olsson.