Thames Water is set to announce a temporary hosepipe ban "in the coming weeks" due to the long-term forecast of dry weather.
The timing was not confirmed "due to a number of operational and legal procedural requirements", the water provider said, adding that customers would be updated at the earliest time possible.
A statement issued by Thames Water this afternoon said the company had been preparing for the summer since winter, filling their reservoirs in London and providing water saving tips.
"Our aim is always to ensure that we will have enough water to supply our customers, regardless of the weather," the statement said.
"Given the long term forecast of dry weather and another forecast of very hot temperatures coming this week we are planning to announce a temporary use ban in the coming weeks."
In the meantime, customers were urged to only use what they needed for their essential use, it added.
The ban will follow the water provider's campaign urging customers to use water efficiently amid a period of dry, hot weather.
It comes as the UK prepares for a heatwave which could reach as high as 35C later this week.
An amber warning for extreme heat is in place in parts of the UK with a heat health alert for central and southern England from Tuesday to Saturday.
The Met Office said there is “very little meaningful rain” on the horizon, with only the North West likely to see short-lived showers.
Deputy Chief Meteorologist Tony Wardle said: “With high pressure dominant this week, the influence of any showers will be contained to the far northwest, and even here will be short-lived in nature.
“Further south, which has seen little rain for some time now, dryness will continue through the week and provide no relief for parched land, especially in the southeast."
The mercury is this week set to climb into the low to mid 30s in central and southern parts of England. though readings will not be as severe as the record-breaking heat of July when they hit 41C, said forecasters.
Using hosepipes has already been banned by two water companies while others have warned they may need to follow suit.
It follows the driest eight months from November to June since 1976 and the most sun-baked July on record for parts of eastern and southern England.
Southern Water has introduced a ban in the Isle of Wight and Hampshire and is asking the Environment Agency for a special permit to allow it to take more water from the River Test, according to The Times.
"The permit would last six months or until flows have returned to above 500Ml per day for 21 consecutive days," a spokesperson said.
Over the summer, the River Test's flow has fallen from 2,500 megalitres (MI) per day in March to just 450MI at present.
The water company has warned that levels could fall even more this month to 365MI – the legal limit for drawing water.
South East Water added that it has been "left with no choice but to restrict the use of hosepipes and sprinklers" - from midnight on August 12 within Kent and Sussex “until further notice".
The firm added that it was taking the step “to ensure we have enough water for both essential use and to protect the environment”, and to enable a reduction in the amount of water “we need to take from already stressed local water sources”.
Scientists have warned that droughts are becoming more likely due to climate change, driven by greenhouse gas emissions from human activities such as the burning of fossil fuels.
