Britain is set to bask in sunshine as temperatures hit 27C, before heavy rain sweeps across the country.
The week will start off warm and dry before temperatures soar on Tuesday, the Met Office said.
Highs of 27C are expected and there is a chance temperatures could climb to 28C In London and Bristol.
The capital and southeast England will get the best of the weather, with a risk of heavy showers in northern parts of the UK.
It comes after Britain recorded its hottest day of the year at the end of June as temperatures rose to 34C in west London.
The heatwave was brought on by an “enormous” bubble of warm air from the Sahara which spread across Europe.
But the sunny weather will not last all week, with thick cloud and bands of rain spreading east from the west of the country on Wednesday.
However, the unsettled weather will be broken up by sunny spells followed by brighter, fresher conditions.
Temperatures will drop closer to average for this time of year, with highs of 24C in London and 20C in Leeds by Friday. But it is likely to feel cooler under the cloud and rain.
The average temperature for July is 19C across the UK and 21C in England.
Moving into the weekend, it is likely to turn more unsettled with rain and stronger winds moving northeast across the UK.
Heavy rain is likely to hit southern and western areas, the Met Office said.
Nicola Maxey, a spokesperson for the Met Office, said: “The start of the week will be fine, dry and sunny across much of the country.
“On Tuesday, there is an isolated chance temperatures will hit 28C in London and the far west of Bristol.
“From Wednesday, the weather will turn more unsettles but there will still be some sunny spells – so it’s not all doom and gloom.
“Although temperatures will feel much cooler under the cloud and rain.”