The met office has issued a new yellow alert for Tuesday, the second in as many days, with temperatures set to rise to 41 C inland — 4 C higher than average for the time of year.
The yellow alert is in force from 1 pm to 5 pm.
In its early morning weather bulletin, the met office said a hot air mass is affecting the area.
Tuesday will be mainly fine with temperatures of 41 C inland, around 32 C on the west coasts, around 35 C on the remaining coasts and around 30 C in the mountains.
Tonight will be mainly fine with temperatures falling to 25 C inland and on the south and east coasts, around 23 C on the remaining coasts and around 19 C in the higher mountains.
Wednesday, Thursday and Friday will be mainly fine with some increased cloud at intervals, mainly from midday on.
Temperatures will remain at the same levels on Wednesday, edging down on Thursday and Friday but remaining above average for the time of year.