London could bask in 27C heat this week, although thunderstorms may break up the pleasant weather.
The Met Office has warned thunderstorm alerts could have to be issued as it forecasts "intense rainfall" across parts of the UK.
The deluge is expected to hit on Wednesday evening, after a drier and widely sunny Tuesday, during which time some western areas could see 20-40mm of rain over just a few hours.
But London is expected to miss the worst of the weather, with uninterrupted sunshine forecast for Wednesday, with similar conditions predicted throughout the week.
Both the Met Office and BBC Weather have forecast that the mercury could reach 27C in London on Friday, with plenty of sunshine.
The BBC has warned that clouds may thicken throughout the day on Thursday and there will be a “risk of heavy, thundery showers in the evening”.
But this could make way for clear skies on Friday and into the weekend.
Temperatures are also forecast to rise further across the south-east and central England, potentially reaching 27C on Wednesday and Thursday and then 29C on Friday.
But a plume of warm air from Iberia and France is set to kick in, bringing the chance of thunderstorms.
Met Office deputy chief meteorologist Mike Silverstone said: "After largely benign weather early in the week, some intense, thundery showers will move in on Wednesday evening.
"These thunderstorms are being triggered by some warm, humid air that is moving into the UK from the south.
"The intense rainfall could see 20-40mm accumulating over just a few hours, which could cause some disruption.
"While there are no severe weather warnings issued at the moment, it is possible thunderstorm warnings may be issued this week."
The thunderstorms and showers are forecast to move north and east through Thursday, with a small reprieve on Friday before another band moves in from the southwest, bringing more rain lasting into the early hours of Saturday.
Mr Silverstone said: "As temperatures rise this week, it is possible heatwave thresholds could be reached in some parts of the UK, particularly the northwest Midlands, north-west England and northeast Wales, however it is very dependent on cloud cover later this week, so it is not a certainty.
"This warm spell will feel different to the fine weather we experienced in May as the humidity will be much higher, making it feel more uncomfortable.
"Additionally, while in May the nights were still fairly cool, overnight temperatures this week are forecast to remain fairly warm, which can disrupt people's sleep."
