LONDON - Parts of Britain on Thursday (April 19) experienced the warmest April day in almost 70 years with temperatures in central London reaching 28 deg C.

The balmy spell peaked in the south-east of England, where it was hotter than Spain and Italy, The Guardian reported.

Temperatures reached 28.3 deg C in St James's Park, central London, and 27.9 deg C in Northolt, north-west London, making it the warmest day of the year so far.

It is also the hottest April day since 1949 when the mercury soared to 29.4 deg C.

The hot spell far exceeds the average maximum temperature for April of 11.4 deg C.

It prompted warnings for competitors in the London Marathon which will be held on Sunday (April 22).

Sunday was not expected to be as hot although forecasts of 23 deg C in the capital would make it the warmest London Marathon on record.

Conditions may be especially difficult for runners in fancy dress on the 26.2-mile (42km) route, organisers said.

The event director, Hugh Brasher, said: "The previous highest temperature on race day was 22.2 deg C in 1996 and 2007. We will continue to monitor the forecast closely as we all know that weather forecasts can change."

The organisers' contingency plans include increasing the supply of water to all drinks stations to enable runners to douse themselves with water, increasing the number of showers on the route and increasing the supply of ice to first aid stations.

The heatwave has come more than a month after Britain struggled with the "beast from the east" - freezing temperatures from late February to March when blasts of icy weather from Siberia engulfed Europe.

The summery spell comes as a result of warm air from the Azores, off the coast of Portugal, being dragged up towards Britain by the combined efforts of an area of low pressure over the Atlantic and high pressure over western Europe, reported The Telegraph.