The Met Office has issued a "risk to life" health warning across six UK regions, as Britain prepares for a blistering second heatwave.
An amber heat health alert has been issued for the South East, South West, East of England, and London regions - being an "enhanced hot weather response".
Meanwhile, a yellow heat health alert has been issued for the East Midlands and West Midlands, as a less severe hot weather response.
Temperatures are expected to widely reach the high-20s, with the potential for 32C to be reached in the south of England on Sunday, and potentially even higher temperatures on Monday.
The Met Office cautioned a rise in risk of death, particularly among those aged 65 and over or with health conditions, and pointed to likely travel delays, and risk of water-related incidents such as cold-water shock and drowning.
The warnings are expected to remain in place until Tuesday (June 23), with experts pointing to soaring temperatures in central and western Europe feeding warmer air towards the UK.
Deputy Chief Forecaster, Gregory Wolverson, said: "This week’s weather reflects a contrast we often see in summer, with more unsettled conditions passing to the northwest of the UK while heat builds in the south and east.
"As we move towards the weekend, we’ll see conditions become more widely settled and temperatures rise all round. Many parts of southern and eastern England are likely to see temperatures high enough to meet heatwave thresholds.
Met Office officials have warned to stay safe in water | GETTY"It’s important to note that while temperatures may be high, we might not all see the wall-to-wall sunshine and blue skies we experienced back in May because there is more cloud around.
"There is also a chance of thunderstorms developing in places, particularly later each day, which could bring heavy showers and localised impacts."
In both the East Midlands and West Midlands, with a risk score of seven, minor impacts are likely, according to forecasters.
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Meanwhile, the South East, South West, East of England, and London - all with a risk score of 12 - are described as likely to expect "significant impacts".
Other regions, including the North East, North West, and Yorkshire and The Humber, have all escaped a heat alert with a risk score of six, whereby minor impacts are possible - but not expected.
Forecasters described "high pressure over mainland Europe will allow increasingly warm and humid air to build across southern and eastern areas, while lower pressure close to the northwest keeps conditions more changeable".
Affected areas include South East, South West, East of England, London, East Midlands and West Midlands
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The Met Office stressed that those heading to the coast should be mindful that sea surface temperatures are not as high as they would be in mid-summer.
The Royal Life Saving Society UK (RLSS UK) have also published accessible water safety resources available, as part of drowning prevention week this week.
Visit metoffice.gov.uk to stay up to date with the latest forecasts, and find extended safety guidance during periods of high temperatures.