Weather: Where UK's 'mini-heatwave' will turn sour this weekend

Heat warnings are in place this weekend for much of England, but the Met Office has warned the weather may take a turn for the worse with thunderstorms likely.

Temperatures are set to increase on Thursday, Friday and again on Saturday when they will potentially hit 29C, according to the Met Office.

But, the weather is quickly set to change as clouds, rain and thunderstorms will sweep in over the weekend, and the nights become humid.

The UK’s weather service issued a yellow thunderstorm warning on Thursday with central and southern England, and the whole of Wales, set for rain and thunder on Saturday.

A change in weather is expected to come at around 2pm on Saturday, with the warning in place until 9pm on Saturday.

What is a heatwave?

Oli Clayden, from the Met Office, confirmed that there could be some travel disruption over the weekend.

He said: “After a prolonged dry spell there is a chance of surface water flooding.

“There could be some surface water issues that could cause travel disruptions as well as the high gusts across parts of the country.”

It is expected that some parts of the UK could see 30-40mm of rain in an hour during parts of Saturday, with hail also expected to hit the UK on Saturday.

The UK Health Security Agency (UKHSA) has also issued a heat health warning for much of the south and east of England.

A heatwave is generally classified when temperatures hit highs of 25C to 28C across a three-day period, although the threshold is different across the UK.

The higher temperatures will be a result of Storm Oscar, which is currently across the Canary Islands, pushing the high pressure further east.

So far the hottest temperature in the UK was 25.1C in Porthmadog, northwest Wales, on 30 May, but Partridge said the country is “certainly” going to see higher temperatures.

He also said the humidity at night will become “uncomfortable” as some areas will not get below 15C or 16C, compared to about 3C at the start of the week.

What areas will experience the heatwave?

The weather is expected to hit the “borderline” criteria for a heatwave, with the southwest of England most likely to see it, the forecaster said.

According to the Met Office, the highest temperatures will be in southwest England and southwest Wales.

From Friday it will get warmer but with more humid air and the risk of showers across southwest England.

The warmest temperature expected on Friday is 26C or 27C, likely in central and southern England.

Saturday will be the warmest day, with forecasters expecting it to reach 27C or 28C, with a small chance of it hitting 29C, north of London.

Which areas can expect a thunderstorm this weekend?

As the weekend arrives, there will be a risk of thunder and showers from the southwest to the northeast.

Wales, London and much of central England are under a yellow thunderstorm warning for Saturday.

Heavy rain is predicted across the same area on Sunday, but no warning is in place.

The Met Office's yellow warning says there is a "small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds."

Much of central England currently looks like it will avoid rain but eastern parts – including, Cambridge, north-east Essex and northern Kent – are expected to be hit by wetter weather.

Temperatures are expected to be in the mid-20s at the same time, before cooler conditions at the start of next week.