The Met Office has upgraded its warning to amber, covering parts of Wales, the west Midlands and the north west of England.

The warning runs from 5.45pm to 9pm and states that "flooding of homes and businesses is likely and could happen quickly", and "fast flowing or deep floodwater is likely, causing danger to life".

It comes as a number of areas across the south east hit 30C on Saturday, with yellow thunderstorm warnings in place for much of the country over the weekend.

Another yellow warning is in place on Sunday from midday to 9pm for Wales, Northern Ireland and most of western and central England and Scotland.

Temperatures are likely to reach 32C by the end of Saturday, forecasters added.

The UK Health Security Agency (UKHSA) has issued an amber heat-health alert for hot weather until 9am on Tuesday in the West Midlands, East Midlands, East of England, South East and South West.

It means the impact of the heat is "likely to be felt across the whole health service… and the wider population, not just the most vulnerable".

Met Office chief meteorologist Frank Saunders said: "As the heat builds from the south, thundery showers will develop through Saturday afternoon.

"While not everyone in the warning area will see the heaviest showers, or even any rain at all, some will bring heavy thundery downpours.

"With intense showers there is a risk of surface water flooding which could cause some disruption.

"Sunday will see 30C (86F) again in parts of southern UK and the risk of thunderstorms more widely - particularly western and central areas."

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Forecaster Tomasz Schafernaker added: "We will notice the humidity rising as we go through the weekend with some really balmy nights on the way.

"At 10pm on Saturday, temperatures in some towns and cities will still be hovering around 20C.

"For Sunday there's a lot of sunshine around, very warm, very humid but with a greater chance of catching showers and thunderstorms across many western parts of the UK… hail, thunder and gusty winds and then it is back to sunshine again."