Residents across parts of the Thames Valley and London could face a hosepipe ban if more rain does not fall across the region, Thames Water has warned.
The company which serves around 15 million people, says it has seen extremely high demand in recent weeks, putting pressure on its resources.
It has warned that its reservoirs are 'below average' for this time of year, mainly due to a lack of rainfall in the last few months.
As well as reservoirs, water is also taken from rivers and underground aquifers, which are also lower than expected.
Thames Water has said that people should use 'water wisely' to ensure supplies can be 'maintained' for all.
Why are suppliers warning of hosepipe bans?
Over May, June and July roughly 65% of expected rain has fallen in across the Thames Valley and London.
This, coupled with the highest demand for water in over 25 years, has put extra stress on the system.
There is only so much Thames Water and other suppliers can take from rivers and groundwater, before it begins to damage the environment and important habitats.
Other parts of the country have already seen a hosepipe introduced, with parts of Hampshire and Berkshire under restrictions from Friday.
Southern Water, the freshwater supplier, said the restrictions were necessary to protect supplies.
When could a hosepipe ban come into force?
Thames Water has not said when a ban could be introduced.
It is purely dependant on how much rain we see in the next few weeks, but after the driest July on record, the company has said above average rainfall may be needed to avoid restrictions.
The Met Office said it has not just been a dry July, but figures also show that England has had the driest eight-month period from November 2021 to June 2022 since 1976, when the country struggled with severe drought.
Over that period, just 16.6in (421mm) of rain has fallen across England – less than three-quarters (74%) of the 1991-2020 average of 22.4in (568mm).
South-east England clocked up 24 days of zero average rainfall between June 1 and July 24 this year, Met Office figures show. In the same period in 1976, the region experienced 36 days without rain.
A Thames Water spokesperson said: “The recent heatwave and extreme heat has resulted in extremely high demand, some of our highest for over 25 years. Our teams have been working 24/7, during incredibly hot conditions, to maintain supplies to customers, ensuring the output of our supply systems are running at maximum capacity.
"At times the demand can outstrip our capacity to treat water and hence we have been promoting the need to use water wisely to ensure we can maintain supplies for all.
“Looking slightly longer term, our reservoirs have fallen below average for this time of year. This is due to the fact that nine out of the last 11 months have been drier than average with underground aquifers and flows in the rivers, which we rely on for water, also lower than expected for this time of year.
"Over the last three months, our area received only 65 per cent of the average rainfall, with similarly low levels of rainfall over the preceding winter and spring period.
“Whilst we’re not currently expecting to need to introduce restrictions on water use this summer, we know the water we have stored in our reservoirs will continue to reduce, so if we do not receive around or above average rainfall in the coming months this will increase pressure on our resources and may indeed result in the need for more water saving measures including restrictions.”