People are being urged to limit their showers to just four minutes after drought was declared in the South East.
Two water companies are sending out waterproof "egg timers" to help their customers spend less time washing.
The prospect of hosepipe bans in the coming weeks is also looming with little prospect of extra rain in the coming months.
On Thursday, temperatures in the UK are set to rise to 16C - the same as in Honolulu - although they will soon fall again.
Sky weather presenter Isobel Lang said: "Once rain has cleared early on Thursday, temperatures should get up to a fairly spring-like 16C in eastern parts, feeling very pleasant in any sunshine.
"It won't last, though, as it will cool down again by the weekend.
"We will need months of rain to correct the problem in the South."
Environment Secretary Caroline Spelman issued the drought declaration at a summit of water companies, farmers and wildlife groups.
She was forced to act after the South East - the most populated area of Britain - suffered two dry winters in a row, leaving water levels worryingly low.
The Anglia region is already in drought, meaning that more than half of the population of Britain faces hosepipe bans in a matter of weeks.
London faces restrictions with extra water being needed because of the Olympics. Most of the Midlands could be declared in drought within the next few weeks.
There are also concerns for wildlife such as kingfishers, water voles and trout. Some rivers and groundwater levels are lower than 1976, when wildlife died of heat stress, wild fires broke out and food prices rocketed.
Following the water summit, Mrs Spelman said the best way to avoid a repeat of that situation was to start saving water now.
"It is not just the responsibility of government, water companies and businesses to act against drought. We are asking everyone to use less water and to start now," she said.
Anglian Water and South East Water , the main water companies in the affected regions, are issuing advice to help save water and giving out the free shower timers.
It is estimated cutting shower times by one minute can save nine litres of water. The average Briton uses 150 litres of water a day but the Department of the Environment (Defra) says this could be cut by at least 20 litres.
Anglian Water has been issued with drought permits to refill two reservoirs and Southern is seeking a permit to help refill Bewl reservoir. Thames wants to pump more water out of rivers.
News that the South East was in drought has brought calls for better management of England's water resources.
Martin Salter, of the Angling Trust , called for more investment in storage reservoirs, universal metering and an end to unsustainable abstraction from rivers.
"Infrastructure investment will need both political vision and courage because it will impact on water bills," he said.
"But we live in a mad world where purified drinking water is used to flush toilets and water golf courses in a country with one of the worst records for extravagant water use in the whole of Europe."