Wednesday was the hottest day of the year, with temperatures hitting almost 90 degrees Fahrenheit -- the first heat wave Britain has experienced in seven years, the BBC of London reported.
Road surfaces melted and railway tracks buckled in the heat in parts of the country this week, causing problems for drivers and train passengers.
Public Health England's heat-wave plan targets health and social care workers, hospitals and care homes, advising them to check regularly on vulnerable patients, and shares sun safety messages, said Dr. Angie Bone, leader of the plan.
"The temperature threshold for the region is for daytime highs of 90 degrees and night minima of 64 degrees over two days and the intervening night," London's Sky News reported, referring to the Level 3 (second to highest) heat-health warning.
The alert followed on the heels of a series of accidents in which people apparently have died trying to cool off.
The bodies of two men were recovered from a Norfolk water location where swimming is banned, and the bodies of a man in his 40s and a teenage boy were found in separate lakes, Sky News reported.