LONDON, Dec. 14 (Xinhua) -- A summer heatwave in Britain when temperatures exceeded 30 degrees Celsius led to hundreds of deaths, a report by the Office for National Statistics (ONS) revealed Friday.

ONS said the exceptionally hot weather experienced on July 26 and 27 coincided with a sharp increase in the daily death count, which substantially exceeded the five-year average on those two days.

The report cited July 27 when there were 251 more deaths than the five-year average number for the same day, with the death count rising well above the maximum number of deaths seen on that day in the preceding five-year period.

This period coincided with the highest reported temperatures of the year in Britain, reaching a maximum of 30.7 degrees Celsius on July 26 and 29.7 degrees on July 27.

In contrast, on July 29, when the maximum temperature was at its lowest for July, there were 114 fewer deaths than the five-year average number for that day. The thermometer recorded 20.3 degrees on July 28 and 21 degrees on July 29.

The ONS report said that Public Health England warn that excess heat-related deaths may begin to become apparent when ambient temperatures exceed 24.5 degrees.

When heatwaves occur it can lead to a temporary increase in deaths among frail individuals who are especially vulnerable, ONS noted.