Sun-worshippers are set for an enforced break from basking in the relentless rays, as thundery showers today begin to move in to drench much of the country.
While the mercury hit 27C (81F) at Heathrow yesterday, forecasters warned today may be time to "put away the flip flops".
Storms are expected to begin battering parched areas of the South and East, although the downpour was already in process in eastern Scotland and the northern Isles yesterday.
But those who have been enjoying the heatwave should take heart: even the unsettled weather of the coming few days will still see "decent" periods of sunshine and temperatures in the mid to high 20sC (high 70s-low 80sF).
Rachel Vince, forecaster at the PA WeatherCentre, said: "Shetland and Orkney are not renowned for thunder storms, but they are getting quite a battering. We have had reports of lightning and locally-heavy downpours.
"We are expecting thundery activity to move up from the South, especially affecting the East and south-east England tomorrow.
"Make the most of today's sunshine - it might not be flip flop weather tomorrow!"
She added that most of England and Wales was facing a more unsettled spell with showers and rain, but "the indications are there will be decent amounts of sunshine. We are not confident when the unsettled spell is going to end, so I wouldn't pack away the bikini just yet".
And while we may have lost the sweltering temperatures that hit a high of 36.5C (97.7F) last week at Wisley, Surrey - smashing the all-time record British temperature for the month - Miss Vince said we are also going to lose the humidity.
Figures released yesterday revealed that the sweltering weather has been bad news for retailers, while power companies are being asked to generate more electricity following a surge in demand as consumers switch on air conditioning systems in a bid to beat the heatwave.
The National Grid said it had issued a Notice of Insufficient System Margin (NISM) to power firms, signalling that additional reserve was needed between the hours of 10am and 1pm.
Last week, the average cost of the wholesale market trebled after a notice was issued due to demand from sweltering customers and a number of power stations being closed for repair work.
The Met Office issued a Heat-Health Watch at level 3 - indicating the probability of heatwave conditions in parts of England and Wales was 100 per cent.