Nearly 700 more deaths than average were recorded during the 15-day peak of the heatwave in June and July in England and Wales, with older people most at risk,according to British official statistics on Friday.

British experts said that an increase in deaths is fully expected during heatwaves, but they cautioned that the provisional data requires further analysis to determine if the higher mortality is statistically significant for the summer months.

Parts of the UK are to bask in temperatures reaching the high 20s and low 30s as Europe braces itself for a record-breaking heatwave.

In the South East the mercury could climb up to 33 degrees Celsius on Friday as sunshine returns to most of the country.

Southwestern parts of the UK could see 28 degrees Celsius or 29 degrees Celsius.

Northern England, Scotland and Northern Ireland could see a scattering of rain but temperatures will reach the mid-20s.

"The heatwave will have been associated with a number of excess deaths," said Dr Adrian Boyle of the Royal College of Emergency Medicine. "The people most at risk in a heatwave are the frail elderly with heart or kidney problems."

The UK is "woefully unprepared" for deadly heatwaves, a cross-party committee of members of parliaments (MPs) concluded in a report published on July 27. The MPs said the government had ignored warnings from its official climate change adviser, and that without action heat-related deaths will triple to 7,000 a year by the 2040s.

The height of the heatwave was from June 25 to July 9, according to the Met Office, a run of 15 consecutive days with temperatures above 28 degrees Celsius. The deaths registered during the weeks covering this period were 663 higher than the average for the same weeks over the previous five years, a Guardian analysis of data from the British Office of National Statistics (ONS) showed.

ONS analysis for previous years indicate hundreds of additional deaths were associated with brief periods of heatwave conditions in July 2016 and June 2017. The full toll of the 2018 heatwave could reach 1,000, according to one prediction.