Millions of people are facing a hosepipe ban, water company United Utilities has announced.
The firm said the move comes after what is believed to be the longest heatwave since 1976 and will affect seven million customers in the North West of England, where the firm provides its services.
The hosepipe ban, known as a Temporary Use Ban, will come into force on Sunday August 5.
The firm said before then customers can provide feedback if they believe they should be exempt.
The ban will apply to domestic customers who get their water supply from United Utilities, with the exception of customers in Carlisle and the north Eden Valley, where supplies remain at reasonable levels.
Martin Padley, United Utilities water services director, said: "Despite some recent rainfall, reservoir levels are still lower than we would expect at this time of year and, with forecasters predicting a return to hot dry weather for the rest of July, we are now at a point where we will need to impose some temporary restrictions on customers.
"It is not a decision we have taken lightly and we are enormously grateful to customers for having helped reduce the demand on our network over the last couple of weeks, but unless we get a period of sustained rainfall before August 5 these restrictions will help us safeguard essential water supplies for longer."
The ban restricts the use of hosepipes or sprinklers for watering private gardens and washing private cars but customers will still be able to water their gardens with a watering can and wash their vehicles using a bucket and sponge, the firm said, which uses a fraction of the amount of water a hosepipe or sprinkler uses.
A hosepipe uses 540 litres an hour, as much as a family-of-four would use in one day, while a sprinkler left running overnight uses as much water as a family-of-four would use in one week, according to United Utilities.
A hosepipe ban can reduce water usage by 5-10%, according to research by United Kingdom Water Industry Research, which in the North West would amount to over 100 million litres per day.
United Utilities said the ban was alongside the company's efforts to maintain essential supplies, including maximising water abstraction from ground water supplies, moving water around its regional integrated network of pipes and running a campaign to encourage customers to use water wisely.
Carlisle district and the north-eastern corner of Eden district are exempt because they receive their water from discrete supply network zones fed by local water sources which have not been so badly affected by the overall lack of rainfall, the firm said.
Water resource levels in these zones are considered adequate but the zones are not connected to the integrated network which serves the rest of the region.
Customers can find out whether they are in an area affected by the ban, and get more information on water saving tips, by entering their postcode into the search facility at www.unitedutilities.com.