Thursday will be another fine day, though increased cloud at midday and in the afternoon may lead to isolated showers in the mountains, the met office said in its early morning weather forecast.
Temperatures will rise to 38C inland, around 35C on the north coasts, around 33C on the southeast and east coasts, around 32C on the southwest coast and around 29C on the west coast and in the higher mountains.
Tonight, there will be increased low cloud at intervals, mainly on the west and south coasts, while later local fog is forecast, mainly in the east. Temperatures will drop to 20C inland, around 21C on the coasts and 19C in the mountains.
Friday and Saturday will be mainly fine, while increased cloud is forecast for Sunday.
Temperatures are expected to remain at the same levels until Saturday, edging down to below the seasonal average on Sunday.