The UK recorded one of driest Junes ever, according to provisional figures, as the heatwave showed few signs of abating.
It was the driest June on record in south-east and central southern England, with just 6% of expected rainfall across counties like Essex and Dorset, the Met Office said.
Scotland also enjoyed its highest ever temperature, with 33.2C recorded in Motherwell on June 28.
The sweltering spell has continued into July, with many parts enjoying temperatures around the mid-to-high 20s.
Tennis lovers looked set for plenty of action as Wimbledon began on Monday, with stars kicking the tournament off on sun-drenched courts.
Meanwhile, utility companies have been pumping billions of extra litres of water to try and keep pace with demand, which has risen by as much as 30%, Water UK said.
But there is no risk of drought, as above-average rainfall in the Spring means water levels are in a healthy position, it added.
There are currently no restrictions in England, but Thames Water says it is funnelling an extra 450 million litres per day as it deals with “record levels” of demand and many suppliers are warning their customers to use water sparingly.
Some households in Berkshire, Wiltshire and Gloucestershire may see low-pressure hit their water supplies during peak hours, it added.
In the Republic of Ireland, a month-long hosepipe ban took effect in the greater Dublin area on Monday as demand continues to outstrip supply across the country.
The weather has been dry since late February in the country, with authorities saying rainfall has been similar to 1976, when a major drought took hold, Irish Water said.
It follows the ban introduced across Northern Ireland last Friday with the public asked to limit tap water use to drinking, cooking and washing.
The bookmakers Ladbrokes had the UK at 4/6 to see 35C during the week.
The heat is an example of “extra volatility” facing food producers, with some arable farmers seeing no recordable rainfall in a key month for their crops, the National Farmers’ Union said.
Across the country, council staff and social workers are making extra calls and visits on the vulnerable and elderly, who are more likely to struggle in the heat, the Local Government Association (LGA) said.
It is part of an “annual heatwave plan”, developed after more than 2,000 people died in England owing to extreme temperatures in 2003, it added.
A level three heatwave health alert was issued by the Met Office for the South West and South East, which is set to last until 9pm on Tuesday.
Izzi Seccombe, Chairman of the LGA’s Community Wellbeing Board, said: “The hundreds of deaths caused by high temperatures each year are avoidable.
“Councils are determined to reduce the toll as much as possible, but they cannot do it alone.
“Local people can make a massive difference by helping us identify other residents who might need some advice or practical help.”