Spring may still be with us but summertime temperatures can be expected this weekend when the mercury is likely to touch 80 degrees fahrenheit and help make it the hottest April on record.

Sunshine and clear skies can be expected across much of Britain today and tomorrow and the weather next week is forecast to be even drier, according to the Met Office, who said there was little sign of the warm spell coming to an end.

Conditions are expected to be so warm that the Department for the Environment Food and Rural Affairs (Defra) has issued its first summer smog warning.

The risk of pollution from low-level ozone clouds formed by the reaction to sunlight of nitrogen dioxide and other substances is described as “high” across England and Wales tomorrow and Monday.

Warm sunny conditions are anticipated over most of Britain over the weekend with just the eastern coast northwards from the Humber likely to suffer cloud, fog and cool weather.

For the rest of the country it is expected to be warmer than usual, especially in the Midlands and Southern England, though sporadic rainstorms could creep in from the south coast.

Barry Grommet of the Met Office said: “It is looking like we will see the hottest temperatures of the year so far.

“I would expect it to be very hot in the Cotswolds and I am sure the beaches in Brighton and Bournemouth will be packed. Generally, it will be around 23C (73F) across England and Wales.

“It could well be as hot as 28C (82F) on late Sunday or Monday in London, the South-east, the West Midlands or Wales.

“The north-eastern coastal areas will not enjoy such good weather because there is high pressure over Scandinavia and the northern North Sea which is bringing easterly winds and sea fog.

“But inland and in London and the South-east and West, there be highs of around 25C (77C) on Saturday, rising through Sunday and Monday.”

Figures released by the Met Office yesterday show that up until April 25 the month was the warmest in 348 years of records.

Mr Grommet said: “With only the weekend to come, the April average is already half a degree above the current record and the weekend is going to be very hot. April 2007 is going to set several records.”

The provisional average temperature for the month is 11.1C, beating the previous highest of 10.6C set in 1865, according to the Central England Temperature (CET) records dating back to 1659.

The rolling 12-month period of May 2006 to April 2007 stands provisionally at 11.6C, exceeding the 11.1C record set in the 12 months ending in October 1995.

The warming trend seen in the CET since the 1980s is consistent with climate change predictions. Dr Debbie Hemming, climate scientist at the Met Office Hadley Centre said: “The effects of temperature rise are being experienced on a global scale.”

April was one of the driest since rainfall records began for Britain in 1914. Only three years have been drier, though low levels of rainfall over the weekend could put it sixth overall.

Only 24.6mm had been recorded on average for Britain by April 25, compared to 14.1mm in 1938, 14.4mm in 1974, 17.8mm in 1980, and 27.5mm in 1984 and 1957.

In Central and South Eastern England just 2.3mm has fallen while in East Anglia there has only been 1.8mm, which is four per cent of the average.

Earlier this year the Met Office said there is a 70 per cent chance that the average temperature between July and August will be above 14.1C (57.4F) including night temperatures. That would make it the ninth year in a row that the season has been hotter than usual.

There is a 12 per cent chance that that summer will match 2003 and 2006 for the severity of heat in Britain while worldwide the Met Office has predicted the hottest year on record.