It will be unseasonably windy, with coastal gales, the Met Office said.
It will also be cloudy with outbreaks of rain, heavy and persistent for some areas throughout the morning.
The Met Office added that there will be brighter spells possible by the afternoon, but most places cloudy with showers, heavy at times and potentially thundery.
The maximum temperature is expected to be 20°C.
The Met Office said showers are likely to continue into the evening, only gradually easing later in the night.
Some parts will stay drier though, especially in the west.
The mnimum temperature is expected to be 13°C tonight.