The met office on Wednesday issued a new yellow alert, warning that heavy thunderstorms, probably accompanied by hail, will affect the area.
Locally, the accumulated precipitation may exceed 50 millimeters in a six hour period, it added.
The yellow alert is in force from 11 am on Wednesday to 11 am on Thursday.
Earlier, the met office said Wednesday will be mainly cloudy with scattered showers and isolated thunderstorms which may be accompanied by hail.
Temperatures will be 19 C inland, around 20 C on the coasts and 9 C in the mountains. Tonight will be cloudy with rain and isolated thunderstorms. Thunderstorms may be accompanied by hail and strong winds.
Thursday will be cloudy at intervals with scattered showers and isolated thunderstorms. There may be hail during thunderstorms.
On Friday, localised increased cloud may lead to isolated showers and/or thunderstorms.
Saturday will be partly cloudy with isolated showers and/or thunderstorms possible. Temperatures will edge down to a little below average for the time of year.