Temperatures are set to hit 30C in some parts of the UK this week.
Highs of 28C can be expected on Thursday before temperatures are forecast to peak at 30C in London on Friday, Met Office meteorologist Jonathan Vautrey said.
Other areas in southeast England will push towards the high 20s on Friday, where the average temperature in July is around 23C.
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“We’re starting to see south-westerly winds come in, that’s bringing in hotter and more humid conditions, particularly in southern areas, we are going to see temperatures climbing again,” Mr Vautrey said.
“Friday is looking to be the peak of the current hot spell. This heat is not going to be as widespread as what we’ve just come out of, areas to the north aren’t going to be seeing the same highs.”
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But the weather is set to turn later in the week, with a chance of heavy rain and thunderstorms across the UK on the weekend, Mr Vautrey said.
Temperatures will start to slowly drop but are still expected to reach 28C or 29C on Saturday and 25C on Sunday.
It comes after temperatures soared past 30C in parts of the UK last week – as the country had its third heatwave of the year.
A yellow thunderstorm warning has been issued for much of Northern Ireland from 11am until 8pm on Thursday, and this unsettled weather is forecast to spread across more of the UK.
Heavy showers and a few thunderstorms may cause some disruption, particularly to travel, with between 30mm and 40mm of rainfall over a few hours in Northern Ireland, the Met Office said.
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Meanwhile, Southern Water has become the latest company to bring in a hosepipe ban as England battles exceptionally dry weather.
Restrictions like watering gardens, filling paddling pools or washing cars would come in for households in Hampshire and the Isle of Wight from Monday, the company said.
Read more:
Extreme UK weather ‘becoming the norm’
East and West Midlands officially in drought – which areas could be next?
Hosepipe bans hit more households – what you need to know
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It has been the driest start to the year since 1976 for England, causing many water companies to bring in hosepipe bans.
Rainfall across England was 20% less than the long-term average for June, the Environment Agency said. This June was the hottest on record for the country.