Bank Holiday Monday, like it seems with every Bank Holiday, sees rain on the way. It pushes in from the west during the day. It's likely to turn heavy on higher ground and by the end of the day some places could see in excess of an inch of rain.
By the end of the day, everywhere will have seen some wet weather and that will hit temperatures with highs of 13-14C. It will also be rather windy around the coasts.
Once the rain clears on Monday it's a return to sunny spells and showers on Tuesday, then high pressure returns to settle things a little during midweek. Temperatures will slowly return to normal in spite of a cool northwesterly breeze.