Lovisa Andersson at the SMHI met office says that temperatures are around 30 degrees Celsius in central Sweden and along the northern coast, so they've issued a class two warning, raising the level from yesterday.
A warning of this level is for when weather can put the public in danger and cause property damage and disruption to society, according to the strict definition.
Another meteorologist, Emil Björck, says it's primarily a health issue. He told public television SVT that they want to make the public aware there will be a longer period of really warm weather. It also gives the health and care sectors more time to prepare, he adds, with the heatwave now lasting for at least five days.
This is the first year that SMHI has used its new heat warning system, which was brought in last year but never used due to cooler temperatures last summer. But the unusually high temperatures aren't expected to last.
By Sunday Sweden is expected to be back to having normal summer heat of around 25 degrees.
But the sunshine has already dried out the ground and vegetation, and there are several forest fires just north of the capital, meaning that smoke could be smelled all the way into central Stockholm.
Lighting fires on the ground in the whole of Stockholm county is now banned - you can only barbecue on a concrete fireplace, with plenty of water handy.
And if you are suffering from the heat in Sweden you could even ask for your money back. That is, if you are a tenant who's suffering from the heat.
If the thermometer shows over 26 degrees over a longer period you could theoretically apply to get a cut in your rent. But the national tenants association says it's not so clear exactly how you qualify for a rent cut.