The hot air mass affecting the area is gradually receding with temperatures set to drop below 40 C, the met office said in its early morning weather forecast.
Thursday will be mainly fine with increased low cloud at intervals in the west. Temperatures will rise to 39 C inland, around 34 C on the south and east coasts, around 30 C on the west and north coasts and around 29 C in the mountains.
Tonight will be mainly fine but there will be increased low cloud in the west and north.
Temperatures will fall to around 23 C inland and on the west coasts, around 24 C on the south and east coasts, around 22 C on the north coasts and 20 C in the mountains.
Friday will be mainly fine, with increased cloud in the mountains and inland from midday on. In the morning there will increased low cloud and patchy fog on the coasts. Temperatures will edge down to close to average for the time of year.
On Saturday and Sunday, clouds that form at midday and in the afternoon are expected to lead to scattered showers and isolated thunderstorms, mainly in the mountains and inland.
There will be increased low cloud and patchy fog at night and in the morning.
Temperatures will edge down further by Sunday, mainly inland and the mountains, remaining at average for the time of year.