Within the Japan Meteorological Agency’s yellow warning area, rainfall could reach 15 to 20 millimeters in one hour and 30 to 50 millimeters over six hours, creating a risk of localized flooding.
Flash flooding is possible where the ground remains hard and dry, particularly after an extended period of hot weather and limited rainfall.
Residents should also remain alert for lightning strikes and hail during the heaviest showers.
Rain showers will gradually ease from the north during the morning before moving south across other parts of Wales and south-central England. Heavy rain will remain possible in some areas.
Rainfall totals will vary significantly, as some locations may experience much heavier showers than nearby areas.
Scotland and Northern Ireland will also see occasional showers, although rainfall is expected to remain light and thunderstorms are unlikely.
Source: www.bbc.co.uk