The Met Office recorded the hottest day of the year on Sunday, overtaking the previous temperature by one-tenth of a degree.
Temperatures reached 24.4C in Plymouth, narrowly topping Saturday's record of 24.3C in Bramham, West Yorkshire.
People headed outdoors in the hot weather to sunbathe, paddle board and wakeboard among other activities.
Met Office meteorologist Jonathan Vautrey predicted more sunshine on Monday, but cooler temperatures.
He said: "Generally, there will be a lot of dry weather around and a good amount of sunshine still. Hazy cloud pushing through at times might make the sunshine hazy in places.
"Temperatures then going to be feeling cooler along eastern coastal areas."
It is understood Wales and south-west England will be warmest on Monday with temperatures possibly reaching 20C.
It follows the news of several water-related deaths this weekend, which have prompted emergency services to issue fresh safety warnings, with people more likely to be near water over the warm bank holiday.
The body of 15-year-old Lewis Michael Kirkpatrick was found in the River Eden in Carlisle at about 1.30pm on Saturday after emergency services received reports that he and three other teenage boys had got into trouble in the water on Friday evening.
A 14-year-old who was airlifted to hospital on Friday remains in a critical condition, while one of the group managed to swim to safety and another was rescued by a member of the public, Cumbria Police said.
Further south, in Devon, two men aged in their 20s died on Saturday after being rescued from the sea off the coast of Oddicombe, Torbay.
Following the incident, Devon and Cornwall Police superintendent Ben Davies said: "With more people likely to be out near water this Bank Holiday weekend, emergency services are urging everybody to be vigilant to the dangers of the coast and follow water safety advice."
On Sunday afternoon, HM Coastguard tweeted: "As we enjoy the warm weather over the next few weeks, please remember and share @RNLI advice - if you get into trouble in the water, Float To Live."
The RNLI launched its Float to Live safety campaign on Wednesday.
One of its water safety experts, Ross Macleod, said: "As we approach warmer weather and enter into the bank holiday and half-term week ahead, we are expecting the coast to be incredibly busy.
"We want to make sure that if an emergency unfolds, people know what to do.
"If you get into trouble in the water - float to live. Tilt your head back with ears submerged and try to relax and control your breathing.
"Use your hands to help you stay afloat and then call for help to swim to safety if you can."