Parts of the UK will experience heavy downpours on Bank Holiday Monday - hours after temperatures exceeded 20C in what is likely the hottest day of the year.
The heavy rainfall will sweep eastwards and is significant enough for four flood alerts to already be put in place by the Environment Agency.
River Thame and Chalgrove Brook in Oxfordshire, River Rhee in Bedfordshire, Hertfordshire and Cambridgeshire, and Lower Frome and its tributaries in Somerset are subject to warnings.