Thursday's high temperature is set to hit 88 degrees, following Wednesday's high of 89 degrees.
The heat wave marks the longest run of hot weather in Britain in more than seven years, The Independent said
Temperatures are expected to remain high until at least the end of next week, and researchers said the number of heat-related deaths could double.
Officials have issued a level-three heat wave alert, which warns social and healthcare workers to focus on the old, young and those with breathing and heart conditions.
Meanwhile, four of Britain's biggest water companies have told customers to cut back and use water wisely, The Daily Telegraph said.
The companies said a jump in demand for the water has led to decreased pressure.
"At peak times of day in certain areas, demand for water has been increasing by between 20 percent and 50 percent. It's like when a sale opens on Oxford Street, there's plenty of stock but lots more people are trying to go through the door at the same time, so there can be a bit of crush momentarily," Jerry White, of Thames Water, said.