The hot, dry weather has left millions of people facing drought restrictions from next month.
The Environment Agency warned people in England to “ use water wisely ” after an emergency meeting looked at drawing up a drought plan.
Swathes of England are already under “prolonged dry weather ” status, with rivers and reservoirs at low levels and reduced water quality.
If there is no significant rain in the next few weeks, many areas will tip into the “drought” stage, which could lead to hosepipe bans and restrictions for farmers irrigating their crops.
Harvey Bradshaw, chairman of the National Drought Group, said: “We can all do our bit by reducing unnecessary water consumption.”
Stuart Colville, of Water UK, said the Water’s Worth Saving campaign provided the public with “helpful hints and tips on how to do their bit”.
England and Wales have had the driest spell since 1976, and farmers are now calling for the Government to “ensure water for food is prioritised”.
Country Land and Business Association president Mark Tufnell said: “The current dry weather comes at a critical time for crops, such as potatoes, salads and vegetables, which need irrigation.
“Cutting supplies now will risk major impacts.”
Fire chiefs have warned that cities need to prepare for wildfires after dozens of blazes last week. David Swallow, of the National Fire Chiefs Council, said: “Services need to recognise the risk they now have. If they don’t, they’re naive.”
The head of London Fire Brigade Andy Roe said fires in the capital last week were “unprecedented”. He said: “I saw stuff that I had not expected to see as a London firefighter.”
London Fire Brigade assistant commissioner Jonathan Smith said the wildfire risk was “immediate”.
On Friday, a hosepipe ban will cover the Isle of Man.
