As temperatures continue to soar, May in the UK began its warmest, prompting warnings of wildfires and the "hidden danger" of open water swimming.

The Metropolitan Office said Kew Gardens, located in southwest London, registered 28 degrees Celsius on Thursday, bringing it above the 27.4 degrees Celsius in Lossiemouth, 1 January before in 1990.

The agency added that temperatures are still climbing, and Thursday was the warmest day of the year, beating the previous 26.7 degrees Celsius on Wesley Hill in Surrey on Wednesday.

The Metropolitan Office said the last month was the clearest April in Britain since its record in 1910, and it was the third-place April on record.

The body of a 16-year-old boy was recovered from the lake, prompting emergency services to warn open water to swim. Nottinghamshire police said the boy had difficulty swimming in Nottingham's Kuwick Country Park on Wednesday night and his body was found hours later.

Ch Insp David Mather said: “While work is being done now to understand how boys are having difficulties, I would like to take this opportunity to emphasize the case to remind people of the devastating consequences of entering open water – whether people do it on purpose or on purpose.

“Like in such a tragic situation, open water can create a fatal hidden danger and I urge anyone who spends any time on or near open water to use this situation to remind you – especially in recent warm weather, we have been experiencing it.”

"This tragic incident is a clear reminder of the hidden dangers of open waters. We urge everyone to take care of the lakes, rivers and other natural waters," said Tom Staples, manager of Nottinghamshire Fire and Rescue Services Group.

London Fire Brigade urged swimming around open water swimming after a 32% increase in water-related incidents last month compared to a year ago.

Patrick Goulbourne, assistant commissioner of the London Fire Department, said: "In hot weather, we understand the temptation of cooling in rivers, lakes or other open waters. But even if the sun is illuminated and sunny, the water temperature can be dangerously cold. The impact of cold water can affect anyone, regardless of fitness or swimming ability.

"This can cause water to be inhaled and drowned in the worst case. Be especially careful near the edge of the water - it's easy to slip or fall without warning. Always think twice before you go. Unlike designated swimming areas, these environments often lack lifeguards and have hidden dangers."

The Royal National Lifeboat Agency issued a similar warning.

Fire service also warns of warm weather, which means the risk of grass and wildfires is "increased" and may be more easily spread during dry times. Temperatures are expected to drop by Friday, and Saturday will bring cooler conditions across the UK to 14c to 18c.

"The temperature will drop slightly tomorrow, from what we see today, there may be 26 or 27 degrees tomorrow in the far southeast of England," Metropolitan Office spokesman Stephen Dixon said on Thursday afternoon.

The RAC also warned drivers on the road, and spokesman Rod Dennis said the collapse was expected to "sky."

“We urge everyone to travel to make sure they and any passengers have enough water to prevent them from getting stuck in traffic or breakdown and wear sunscreen, hats or umbrellas with them to protect themselves from sunlight,” Dennis said. “If a low coolant lamp appears on the dash, you must avoid driving because the engine has a serious risk of overheating.”

The NHS also reported that searches for hay fever recommendations from Monday to Wednesday have doubled.