It said they may cause localised flooding and disruption.
The forecast for the region said thunderstorms could come any time between midday and 9:00pm as the district begins what is set to be a wet week.
The Met Office warned any heavy downpours could flood roads and make driving conditions difficult.
Temperatures today are set to peak at 17 degrees.
Tuesday and Wednesday will be slightly warmer at 20 and 19 degrees, respectively with light rain changing to cloudy by late morning.
Sunny intervals and light showers are forecast for Thursday and Friday.