A very large area of land is covered by the warning: Götaland, Svealand and southern Norrland.
In the eastern parts of Götaland and Svealand, however, the risk is lower and no warning has been issued.
In Huskvarna, large amounts of rain fell on Friday afternoon, which, among other things, led to a grammar school being flooded.
Several alarms about flooded basements have also come in Jönköping and Habo, among others.
In connection with the rainy weather, there is also a risk of thunder.
In Dalarna, the emergency services have responded to several alarms about lightning strikes.
Among other things, two villas are said to have been struck by lightning.
Several fires are also said to have occurred in connection with impacts.
There are no reports of personal injuries in connection with the events.
Heading north
Most precipitation will probably fall inland, for example around Lake Vänern, according to SVT's meteorologist Maria Augutis.
However, it is difficult to say exactly which places will be hit hardest by the downpours.
The downpour-like rain looks set to continue overnight into Saturday and then move north.
A warning has been issued for Saturday, which also includes northern Jämtland and southwestern Lapland.
Hail weather on Thursday
On Thursday, Båstad was hit by heavy precipitation in the form of hail and rain.
According to the rescue service, damages worth millions of kroner were caused.
- I have never seen anything like this, said Pelle Pettersson, rescue manager in Båstad, earlier to SVT Helsingborg.
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Eva Kjällsdotter had to have help to wade across the street to her car when the rain chaos hit Båstad - hear her story and watch videos from the evening in the clip above.
Photo: Private/SVT