Temperatures towards the end of the week and into the weekend could reach 'lethal' highs, according to experts.
The second heatwave of the summer could see temperatures reach 35C after last month saw an unprecedented 40C spell.
While the mercury isn't set to soar quite as high, the Met Office has issued an extreme heat weather warnings ahead of Friday and Saturday - when temperatures are expected to peak.
The warnings are set to apply from Thursday to Sunday for large parts of southern England, border areas of Wales and the Midlands.
The alert from the national forecasting agency means adverse health effects are "likely to be experienced by those vulnerable to extreme heat", as delays for road, rail and air travel are also possible.
Experts have warned of increased deaths as temperatures could become "lethally hot" - especially for those more vulnerable.
Hannah Cloke, Professor of Hydrology at the University of Reading said: "This summer in the UK is proving to be lethally hot.
"We know that the most dangerous heat conditions are caused when people, particularly those with underlying health conditions, have no respite from the heat for days and nights on end."
As drought warnings are issued across the country, the Liberal Democrats have urged the government to issue an official emergency.
The declaration would see a cabinet minister take responsibility for ensuring rivers, chalk streams and reservoirs do not dry up.
The party has also called for a strategy to ensure farmers can water their crops, and make sure resources are directed to parts of the country which have the least amount of water.
Environment secretary George Eustice implored water companies to make efforts to protect essential supplies as the country moves into “a likely very dry autumn.”
The Met Office has also raised the Fire Severity Index to exceptional – the highest level – for much of southern England, and stretching as far west as Abergavenny in Wales, for this coming Sunday.
Met Office meteorologist Marco Petagna told the PA news agency that the risk of wildfires was very high.
He said: “The risk is very high across much of central, southern and eastern England.
“Going into Friday and the weekend, it starts to increase further, going into the highest category of exceptional risk.”
Mark Hardingham, the chairman of the National Fire Chiefs Council (NFCC) told The Telegraph that he “can’t remember a summer like this” in his entire 32-year career in the fire service.
He said: “We’re not going to see temperatures as hot as we saw three weeks ago, but that doesn’t matter because the ground couldn’t get any drier than it already is.”
UK weather forecast:
Headline:
Sunny and hot or very hot away from northern Scotland.
This Evening and Tonight:
Most areas clear, temperatures falling away in many rural areas, less so for coastal and urban locations. Patchy fog later, mainly across eastern England and Northern Ireland. Parts of northwest and northern Scotland seeing occasional rain, drizzle and low cloud.
Thursday:
Much of England and Wales, plus eastern parts of Northern Ireland and Scotland, sunny and hot or very hot. The far north and northwest of Scotland, cloudier with occasional rain.
Outlook for Friday to Sunday:
Dry, sunny and hot for most; locally very hot. Cooler near some eastern coasts and also the far north, where cloudier with light rain at times. Some showers possible Sunday.
