Weak low pressure is affecting the area.
Saturday will be mainly fine, but clouds that form later in the day may lead to isolated showers or thunderstorms in some mountains areas and some areas inland, the met office said.
Temperatures will rise to 35 C inland, around 30 C on the west coast, around 30 C on the remaining coasts and 25 C in the mountains.
Tonight will be mainly fine but there will be increased low cloud at intervals mainly on the west coast. Temperatures will fall to 21 C inland and the north coast, around 22 C on the remaining coasts and around 15 C in the mountains.
Sunday and Monday will be mainly fine with increased cloud at intervals at midday and in the afternoon which may lead to scattered showers in the mountains and inland in the afternoon.
Tuesday will be mainly fine.
Temperatures will edge up on Sunday, mainly inland and in the mountains but will range to close to average for the time of year.
There will be a further rise on Monday and Tuesday to above average for the time of year.