Isolated rain and storms are expected on Sunday afternoon, the met office said.
It did not exclude the possibility of hail in some areas.
Temperatures will stand at around 32C inland, around 30C on the south and east coasts, 28C on the west coast and around 21C in the mountains.
Sunday night, temperatures will drop about 20C inland 22C along the coast and 13Cs in the mountains.
On Monday, the weather will be mostly cloudy but by noon, isolated storms can be expected mainly in the mountains and inland. Tuesday and Wednesday will also see mostly cloudy.
Temperatures will rise slightly on Monday, with no significant change expected on Tuesday and Wednesday, and will be close to average temperatures for the time of year.