A four-day "extreme heat" warning has come into force in parts of England and Wales, with temperatures poised to exceed 35C in another heatwave that could pressure water supplies and transport services.

The UK Met Office said its amber warning, its second-most severe after red, will last until the end of Sunday, and cautioned that people vulnerable to extreme heat could face adverse health effects.

Temperatures are expected to peak at 35C tomorrow and may hit 36C in some places on Saturday.

The warning follows the driest July for England since 1935, when temperatures rose above 40C for the first time, turning a renewed spotlight to the impacts of climate change.

During July's heatwave, Britain faced power outages, damage to airport runways and rail tracks and dozens of blazes in London, where the fire brigade faced its busiest week since World War II.

Several water companies have already imposed restrictions on water usage and supermarkets have limited sales of disposable barbecues that firefighters warn can set light to tinder-dry grass.

This week's amber warning follows Britain's first-ever red "Extreme Heat" warning in July.

It comes as temperatures are expected to reach 30C in some parts of Leinster and Munster today, according to Met Éireann.

Other European nations have also faced a scorching heatwave in recent weeks with temperatures often exceeding 40C.

More than 1,000 firefighters backed by water-bombing aircraft are battling a "monster" wildfire near France's wine-growing heartland of Bordeaux for a third day today, with no let-up in blistering temperatures seen before the weekend.