Water companies are reminding people to save water with short showers and avoid using hosepipes as demand continues to surge in the dry weather.
While there have been isolated showers in some areas of the UK, Met Office forecasters said the warm weather was continuing for much of the country, with "no real signs" the hot spell was going to finish in the coming days.
Yorkshire Water said daily water consumption was up in its region by up to an extra 200 million litres, and it had enacted its contingency plans to increase water production capacity.
While reservoir levels are nearly three-quarters full and there were no water supply shortages, there is no rainfall expected this week and people should conserve water to ensure the "massive demand" can continue to be met.
Pamela Doherty, director of service delivery at Yorkshire Water, said: "Despite there being no current water shortages, water is a precious resource and we would still encourage everyone to do their bit to help by using water a little more efficiently.
"Our top tips are to limit time spent in the shower to no more than four minutes, use a watering can to water garden plants, and to hold off on cleaning the car but if you have to wash it use just a bucket and sponge."
Customers in some areas of the country have seen low water pressure or a loss of supplies as water companies battle to pump enough water to meet demand as people try to keep cool and water their gardens in the heatwave.
Severn Trent Water been putting water directly into the pipes from tankers and providing bottled water stations in areas such as the High Peaks to deal with loss of supplies and keep water flowing in the face of high demand.
Met Office forecaster Craig Snell said the warm and sunny theme was continuing, although the areas seeing the highest temperatures would shift towards the end of the week and the weekend.
South western England and south Wales had seen some showers and there would be scattered rain - some of it thundery - in the southern UK on Thursday, he said.
But he said: "Even if you see some rain it's not really beneficial rain, for example for farmers. It's short and sharp and not really helping much."
"If you don't like the rain, there's not a lot of rain in the forecast, if you are crying out for rain unfortunately there's nothing really wet heading in our direction."
At the weekend Northern Ireland and Scotland might see some "bits and pieces of rain" but it would be a hot, dry and sunny weekend in England and Wales.
"There's no real signs for the weekend the hot spell is going to finish.
"It's a warm weekend, and that will last at least into Monday next week," he said.
National Farmers' Union deputy president Guy Smith said this year's weather had been "unusual", from an extremely wet winter and spring, to a month where there has been very little rainfall in some areas.
"A lack of rainfall will mean poor grass growth for livestock and dairy farmers, and some arable farmers will have seen no recordable rainfall in a key month for their crops.
"Growers of irrigated crops currently have sufficient access to water to grow our fruit and vegetables, however abstraction restrictions may become inevitable in some catchments," he said.