Temperatures could soar to a record-breaking 34C in part of the UK as Britain continues to bake.
Making the most of the sun before thunderstorms strike
South Midlands may see the hottest July day on record for the UK, according to forecasters.
The countrywide heat wave is expected to cool down slightly with the arrival of thunderstorms on Wednesday while temperatures will still be in the mid 20s.
The highest temperature on Monday was recorded in Cardiff with 33C - just one-tenth of a degree off breaking the record for the hottest July day.
Blaenau Ffestiniog in north Wales did break its own record for its hottest July day, reaching 30C on Monday, BBC Weather forecaster Peter Gibbs said.
Central London sweltered with 29C, Manchester and Glasgow reached 28C and Belfast 22C.
But spare a thought for the coldest place in the country on Monday where it was a mere 15C off the north coast of Scotland.
According to weather proverbs, whatever weather occurs on 15 July - Saint Swithin's Day - will continue for the next 40 days.
That is unlikely to happen this year. By Wednesday umbrellas will be replacing sunhats as dramatic thunderstorms with lightening displays begin to push up from the south.
The downpours will last for much of the day and by the end of the week gardens throughout the whole country will have had a good watering as the storms move north, the BBC's Peter Gibbs said.
While the thunderstorms will cool down the temperature to mid 20s, the thermometer could still creep up later in August, traditionally the hottest month.