Millions of people face hosepipe bans as low-water levels and tinder-dry conditions continue across the UK.
An official drought has been declared in parts of south-west England, parts of southern and central England, and the East of England.
The move is expected to trigger stricter controls on water use, after Yorkshire Water earlier became the fifth water company to announce a ban.
The Environment Agency (EA) said essential water supplies were safe.
Members of the public and businesses in drought-affected areas are being urged to use water wisely following the driest start to the year since 1976.
The last time a drought was announced was in 2018, when hosepipe bans were put in place by water companies across the country.
A four-day amber warning for extreme heat from the Met Office is in place for many parts of England and Wales until Sunday.
Ongoing dry conditions, combined with July’s record-breaking heatwave, have depleted rivers, reservoirs and aquifers – leading to a number of water firms bringing in restrictions.
John Curtin, director of operations for the EA, said the drought would go on for “a long time” as he warned there may be restrictions on crop growing and more bans brought in if conditions continue.
Experts are warning that the dry spell could last for several more months, with analysis from the UK Centre for Ecology and Hydrology (UKCEH) showing that low or even exceptionally low river flows and groundwater levels will probably continue until October in southern England and Wales.
The decision to declare a drought was taken after a meeting of the National Drought Group, which is made up of government and agency officials, water companies and groups including the National Farmers’ Union (NFU).
Drought is decided area by area, and announcing one means government and water companies will launch plans to deal with it, with measures including hosepipe bans and taking more water than usual from rivers.
Wales Drought Liaison group, including environment, health and water professionals, is also looking at the effect of the prolonged dry weather.
Yorkshire Water, which has more than five million customers, says that parts of the region have seen the lowest rainfall since records began more than 130 years ago.
Elsewhere, Hampshire and the Isle of Wight are under a hosepipe ban, while Welsh Water is implementing a ban from 19 August.
Thames Water is also set to follow suit with its own restrictions in the coming weeks.
But Cathryn Ross, strategy and external affairs director for the firm, told BBC Breakfast earlier a ban would probably come in immediately after drought status was officially declared.
Neil Dewis, director of water at Yorkshire Water, said rivers and reservoirs in the region are running at 20% lower than expected for this time of year.
The firm had been “doing everything we can to avoid putting in restrictions” but they were now necessary, he said.
South East Water, whose ban came into force on Friday, is asking people to observe restrictions on using hosepipes, or similar implements such as sprinklers, to water plants, wash the car and fill a paddling pool – with rule-breakers facing a fine of up to £1,000.
The company said its underground water aquifers were below average for the time of year across Kent and Sussex and its raw water reservoirs were also at a lower level.
Dominic Gardener a farmer in West Sussex told the BBC the dry weather was posing many challenges for farmers.
“Everything is starting to struggle a bit – our grass is not growing at all – and livestock, we’re having to feed them extra food,” he said, adding crop yields had also been reduced by the dryness.
About three billion litres of water is lost to leaks each day in the UK – accounting for between 20% and 24% of the total water supply.
Alastair Chisholm, from the Chartered Institution of Water and Environmental Management, told BBC News that the “Victorian era” system needed more investment to bring that figure down, but added that there was an “improving picture.”
Meanwhile, the four day amber extreme heat warning is in place for southern and central England and parts of eastern Wales until Sunday, with warnings of impacts on health and possible travel disruption.
Met Office chief meteorologist Andy Page said UK temperatures had been rising day-on-day through the week – with a peak of 35C expected on Friday and possibly 36C over the weekend.
There will be “increasingly warm nights” with temperatures not expected to drop below the low 20s in some places in the south, he said.
Temperatures are forecast to be lower early next week and the Met Office has issued yellow thunderstorm warnings for Monday covering most of England, Wales and Scotland.
The situation in the UK is being mirrored across Europe. Much of the continent is baking in record heat, exposing riverbeds and triggering restrictions on water use in many areas.
The Met Office’s fire severity index, which assesses how severe a blaze could become, is currently “very high” for most of England and Wales.
The situation facing firefighters across the UK has been described as “unprecedented”, with increasing numbers of wildfires.
Heatwaves are becoming more likely and more extreme because of human-induced climate change.
Research institute UK Centre for Ecology and Hydrology (UKCEH) said it would require “exceptional” rainfall over the next one to three months to bring river, reservoir and groundwater levels back up to normal.
But scientists have warned bouts of heavy rain after a prolonged period of hot weather can cause flash flooding.
Robert Thompson, a professor of Meteorology at the University of Reading, told BBC News “the ground has effectively become like urban concrete” and will not absorb water quickly enough to cope with longer showers.
What is a hosepipe ban?
Restrictions on usage during hosepipe bans can vary between water providers but generally people are not allowed to use hosepipes or anything that connects to a hosepipe or an outside tap.During a ban, people cannot use a hosepipe to:
- Water a garden or plants
- Fill a paddling or swimming pool
- Clean a car
- Fill a pond
- Clean walls or windows
But you can use other water sources, like using your mains water supply but with buckets or watering cans instead of hosepipes, or using stored rainwater from a water butt and there are some exceptions when a hosepipe can be used.
Anyone breaking the rules could face a fine of up to £1,000.