Thunderstorms have been unloading 'heavy downpours' across the south before a heatwave begins.

Flooding and train cancellations hit parts of England at the start of a week in which temperatures are expected to rise above 30C.

Almost half a month's worth of rain fell in just a few hours in some areas on Tuesday morning, with Kent and Sussex being the worst-hit.

READ MORE: London prepares for highs of 35C as 'heatwave' looms

Despite the wet conditions it was a warm and muggy night for many, with temperatures of 20C in some parts of the South East.

Following the downpours, temperatures are expected to build as the week progresses and warm air moves across the Channel.

Public Health England warned that the heat could bring health risks to the elderly and people with underlying health conditions.

READ MORE: UK heatwave: What the law says about workers' rights when it's hot