The Met Office has issued a yellow alert for Tuesday, warning of thunderstorms, probably accompanied by hail.
It said the locally accumulated precipitation may exceed 35 millimetres per hour.
The yellow alert is in force from 11 am to 7 pm.
Meanwhile, in its early morning weather bulletin, the Met Office said that an unstable air mass is affecting the area.
Tuesday will start off partly cloudy with isolated showers but will soon become mainly cloudy with local rain and isolated thuderstorms.
Locally, the phenomena may be intense and thunderstorms may be accompanied by hail.
Temperatures will rise to 25 C inland, around 22 C on the coasts and 14 C in the mountains.
Tonight will become partly cloudy with the possibility of isolated showers initially. Temperatures will fall to 11 C inland, around 14 C on the coasts and 6 C in the mountains.
Wednesday and Thursday will be mainly fine, however there will be increased cloud at intervals.
Friday will be mainly fine, however clouds that develop are expected to lead to isolated showers or thunderstorms, mainly in the mountains and inland.
Temperatures will edge up on Wednesday to close to the seasonal average, and will then edge down a little.