Britain officially declared a drought in parts of England on Friday as households faced new water usage restrictions during a period of prolonged hot and dry weather that has already severely tested the nation's infrastructure.

Parts of southern, central and eastern England are now in drought status, meaning that water companies will step up efforts to manage the impact of dry weather on farmers and the environment, the Environment Agency said in a statement.

"All water companies have reassured us that essential supplies are still safe, and we have made it clear it is their duty to maintain those supplies," Water Minister Steve Double said, following a meeting of the National Drought Group.

"We are better prepared than ever before for periods of dry weather, but we will continue to closely monitor the situation, including impacts on farmers and the environment, and take further action as needed."

The meeting followed what was the driest July in England since 1935. Only 35 per cent of the average rainfall for the month fell, and parts of England and Wales are now in the middle of a four-day "extreme heat" alert.

The last drought in England was 2018.

When the dry weather breaks early next week, rain and thunderstorms mean there is a small chance of flooding in some parts of the country, the Met Office national forecaster said on Friday, issuing a warning for Monday.

Hosepipe ban

Much of Europe has faced weeks of baking temperatures that have triggered large wildfires, drained water levels of the Rhine River in Germany and seen the source of Britain's River Thames dry up further downstream than in previous years.

Earlier on Friday, Yorkshire water announced a hosepipe ban would begin on August 26, forbidding customers from using hoses to water gardens, wash cars or fill up paddling pools.

"The hot, dry, weather means that Yorkshire's rivers are running low and our reservoirs are around 20% lower than we would expect for this time of year," Yorkshire Water's director of water, Neil Dewis, said.

The company, which services about 2.3 million households and 130,000 business customers across northern England and parts of the Midlands, is the latest regional water firm to announce usage restrictions.

A ban on hoses and sprinklers for South East Water customers came into effect on Friday. Thames Water, which supplies 15 million people around London, has said it is also planning restrictions.