Health services should be on alert for a potential heatwave hitting southern England and the Midlands early next week, the government said yesterday.

Temperatures are expected to rise over the weekend and could hit 32 degrees Celsius in London on Monday and Tuesday, with night-time temperatures no lower than 19 or 20 degrees.

Other areas could see daytime temperatures of between 29 and 30 degrees, falling to at least 15 to 18 degrees at night, according to the Met Office.

The forecast has triggered the "amber" alert level 2 in the government's Heatwave Plan, meaning there is a 60 per cent risk of high temperatures being reached in one of more regions on at least two consecutive days and the intervening night.

London, eastern England, the southwest, the southeast and the Midlands are the most likely areas to be affected. "Keeping the home as cool as possible during hot weather and remembering the needs of friends, relatives and neighbours who could be at risk is essential," said the Department of Health.

"The elderly and those who are ill are particularly vulnerable during hot weather, and the most oppressive conditions occur in our towns and cities."

Heat can make heart and respiratory problems worse, and in extreme cases can lead to potentially fatal heat stroke, it said.