Temperatures are expected to rise slightly this week on Wednesday and Thursday above seasonal averages, the met office said.
On Monday the temperature will be around 37C inland, 31C on the west and southwest coasts, 33C along south and east coasts and 27C in the higher mountains.
They will fall at night to 21C inland, 23C along the coast and 17C in the higher mountains.
Tuesday will see temperatures around the same with some increased cloud in the west and in the mountains.
The temperature is not expected to change appreciably on Tuesday, but a slight rise is expected until Thursday that will fluctuate slightly above the the average.