Friday will be mainly fine, but increased cloud after midday may lead to isolated showers, mainly in the mountains, the met office said.
Temperatures are set to rise to 37C inland, around 30C on the coasts and 17C in the mountains.
The wind will be initially south-westerly to north-westerly, weak, and locally up to moderate, 4 to 5 Beaufort, gradually becoming mainly north-westerly to north-easterly and locally in the north, south-westerly, weak 4 to 5 Beaufort.
On Friday temperatures will drop to about 23C inland and on the coasts and around 17C in the mountains.
The forecast for the weekend is similar with mainly fine weather and increased cloud in the afternoon, mainly in the mountains in the afternoons.
By Monday the temperature is expected to gradually rise, fluctuating between close to and slightly above average for the season.