SMHI (which stands for Sveriges meteorologiska och hydrologiska institut) had already flagged that temperatures will exceed 30C for several consecutive days in parts of the Blekinge and Kalmar regions.
Nights are also expected to be uncomfortably warm.
The heat warning, now upgraded to orange, for these areas as well as parts of Kronoberg and Skåne remains in place from Thursday through to Sunday evening, where temperatures may reach 35C.
A yellow alert also warns of high temperatures across large parts of the rest of Götaland from Friday through to Sunday.
This warning stretches from Sjöbo in the south up to Skövde and Linköping.
However, at the start of next week, rain is expected to move into Sweden from the south-west, bringing cooler weather to the entire country.
Are you a bit confused about why even 25C temperatures are considered a heatwave in Sweden? We explain here.