With temperatures in London matching Sunday's record for the hottest day of the year, forecasters predicted even higher levels today.
Yesterday was the warmest day of the year so far in England and Wales with a top temperature of 81F.
But the fine weather brought misery for millions of hay fever sufferers. Counts soared across the country - a pollen count of over 50 is regarded as high - reaching 559 on the Isle of Wight, down from 622 on Sunday.
Dr Jean Emberlin, of the pollen research unit at the University of North London, said the heat wave could not have come at a worse time for sufferers. 'It has been an excellent spring for grass growing - warm and wet - and then with this lovely weather at the weekend the counts surged,' she said. High counts could be expected through June and the first weeks of July as long as the weather remained good.
The high temperatures caused the M11 southbound near Stansted airport, Essex, to be closed after the road began to break up and lift in the heat. Diversions were set up and police said long delays were expected.
Good weather and school holidays increased the number of people visiting London Zoo yesterday. Visitors were unaware that keepers had to cover rhinos with moisturising cream to stop them getting sunburnt.
Originally from East Africa, the rhinos are unused to so much direct sunlight because their natural habitat provides them with shelter. Without protection at the zoo the two four-year-old black rhinos had to be covered with skin cream.
The Met Office warned that thunderstorms, expected on Wednesday, would probably end the fine spell.