Eight areas of England are formally in a drought due to high temperatures and low rainfall.
Devon and Cornwall, Solent and South Downs, Kent, south London and East Sussex, Herts and north London, East Anglia, Thames, Lincolnshire and Northamptonshire, and the East Midlands are all in drought, according to the Department for Environment, Farming and Rural Affairs.
Members of the public and businesses in affected areas are being urged to use water wisely.
A drought is a prolonged period of water shortage, which occurs after long stretches of little or no rain.
"All water companies have reassured us that essential supplies are still safe," Water Minister Steve Double said in a statement.
"We are better prepared than ever before for periods of dry weather, but we will continue to closely monitor the situation, including impacts on farmers and the environment, and take further action as needed."
By this afternoon, temperatures are to soar as high as 35C in southern areas of the UK, which will be hotter than the Bahamas, Jamaica and Barbados.
An amber warning for extreme heat from the Met Office is in place for much of England and Wales until Sunday, with warnings of health impacts and disruption to travel.
The National Drought Group, made up of senior decision makers from the Environment Agency, government, water companies and key representative groups, joined by Water Minister Steve Double, met today to discuss the response to the driest summer in fifty years and the continued action needed.
The group discussed the current outlook and the associated risks and impacts and agreed to further collaborative work across sectors to balance water needs and conserve water.
At the meeting, the Environment Agency said that the drought trigger threshold had been met to move parts of the South West, parts of Southern and Central England, and the East of England into drought.
The triggers used to confirm today's move to drought status for these areas include the hydrological position (including rainfall, river flows, groundwater levels, reservoir levels, and the dryness of soils), as well as the impacts these conditions have on public water supply, abstractors (including farmers) and the environment.
This is determined by the Environment Agency at a local level, rather than nationally.
Forecaster Craig Snell said: "It's going to be an incredibly hot day, and very sunny across the board, with temperatures slightly higher than what we saw on Thursday."
There is also a heat health alert in place from the UK Health Security Agency, with experts advising people to look out for those who are older or with existing health conditions, as well as young children.
The ongoing dry conditions, combined with last month's record-breaking heatwave, have depleted rivers, reservoirs and aquifers and dried up soils, hitting agriculture, water supplies and wildlife and raising the risk of wildfires.
Harvey Bradshaw, Environment Agency executive director for the environment and chair of the NDG, said: "The current high temperatures we are experiencing have exacerbated pressures on wildlife and our water environment.
"EA staff are doing an excellent job responding to environmental impacts and working with water companies to make sure they are following their drought plans.
"Today’s meeting has helped to build on our coordinated action to manage water supplies, consider water users and protect the environment. We urge everyone to manage the amount of water they are using in this exceptionally dry period."
Thames Water earlier said it is "ready to go" on announcing a hosepipe ban if a drought is declared, its strategy and regulatory affairs director has said.
Cathryn Ross said there is a process for introducing a ban but that could be bypassed if an official declaration of drought is made on Friday.
She told BBC Breakfast: "We have to wait and see what the Government says and exactly what that means, possibly even later today. I don't know, we will obviously consider that.
"But, as you probably noticed, at Thames Water we've been asking our customers since late May to respond to the hot weather, to respond to the dry weather and just really take steps to use water wisely."
Asked if a drought was declared, whether the hosepipe ban could come in straight away, she said: "Very probably, yes. We are ready to go with our hosepipe ban.
"Obviously before we introduce the ban itself, we need to be really ready with all of our communications for people right the way across the region, so we're really clear for everybody what they can do, what they can't do, and if they're having any issues how to contact us. We are ready to do that."
Some water companies have failed to meet their own targets for cutting household leaks and domestic use, with many blaming the coronavirus pandemic as more people have been at home.
Ofwat, the water regulator. said in a statement: "Progress has been made in the past few years but there is much further to go, which is why we are pushing companies to reduce leakage, fix their environmental performance and become more financially resilient while keeping bills affordable and helping customers reduce their consumption.
"Where we find that companies have fallen short, we will act - over the last five years, for example, we have imposed penalties and payments of over £250 million."
It comes after temperatures reached 34.2C at Wiggonholt, West Sussex, on Thursday afternoon, while many areas in southern England and Wales hit the low 30s.
Fires broke out in different areas, including London, Essex, Gloucestershire, Surrey and Cheshire.
The Department for Environment, Food and Rural Affairs said today: "Essential supplies of water are safe. Water companies have a duty to ensure these supplies and have reassured regulators and Government that they will remain resilient across the country.
"Defra and the Environment Agency are urging water companies to continue with their precautionary planning to protect essential supplies in the event of a dry Autumn."
