Temperatures are set to soar to sweltering highs up to 33C after the Met Office issued an unprecedented heat warning.
Parts of the UK could reach the blistering high between Tuesday and Thursday, which is hotter than top European holiday destinations such as Marbella, Mykonos and Tenerife.
The mercury will remain above 31C (87.8F) during the week, with forecasters predicting the next few days could be the hottest of the year.
It comes after the Met Office issued its first ever "amber extreme heat warning".
The warning - which is similar to those issued when heavy rain or snow is forecast - covers a large part of Wales, all of south-west England and parts of southern and central England, and will remain in force until the end of Thursday.
Forecasters have warned people to stay out of the sun during the afternoon, close their curtains to keep living rooms cool, stay out of direct sunlight and drink enough water.
Public Health England (PHE) also issued a heat-health alert, warning members of the public to take measures to stay cool and look out for vulnerable people.
Marco Petagna, a Met Office forecaster, said: "We have an amber extreme heat warning in place until Thursday.
"Temperatures are likely to peak at around 32C (89.6F), even reaching 33C (91.4F) in isolated spots across southern England, so very warm for many.
"Even the more cooler areas will see temperatures in the twenties while other places could see some thundery showers."
Mr Petagna put the warm weather down to an area of high pressure above the UK.
He added: "I'd say people should stay out of the midday sun, apply sunscreen when outside, be wary of any health issues you may have and make sure to stay hydrated.
"As this heat remains in place, people will be vulnerable to dehydration, fatigue and nausea, so make sure to stay safe on public transport and if you are heading to the beach."
UK Weather Forecast
Today:
Good deal of cloud affecting coastal districts in the north, whilst other areas will have a good deal of sunshine and turning hot again across central, southern and western parts. Risk of thunderstorms developing over eastern areas of England later.
Tonight:
Heavy showers and thunderstorms over east and southeast England slowly fading, then dry with clear periods, but low cloud and hill fog affecting northeast England and eastern Scotland.
Wednesday:
Another dry and sunny day for many areas, once low cloud clears back to the coast in the north-east. The high temperatures may trigger isolated heavy showers in the afternoon.
