The number of water-related deaths during the UK’s recent heatwave has risen to 11 after the bodies of two teenage boys were recovered in Kent and Oxford.

Emergency workers recovered the body of a 14-year-old boy from the River Thames near Donnington Bridge, Oxford, at about 5.30pm on Wednesday. Thames Valley police said the boy’s family had been informed and that his death was being treated as “unexplained but not suspicious”.

The body of the other boy was recovered from a pond in Swanscombe, Kent. His death was also not being treated as suspicious.

There have been several similar deaths thought to be linked to outdoor swimming in the record-breaking heatwave, during which temperatures climbed to 35.1C at Heathrow and Kew Gardens, in west London, on Tuesday.

The Royal Life Saving Society UK has issued a plea for members of the public to “stop and think” before getting into the water. “Warmer weather unfortunately sees an increase in accidental drownings,” it said.

The hot weather is expected to continue in the coming days, before easing over the weekend, according to the Met Office. A yellow heat health alert has been issued by the UK Health Security Agency for eastern and south-east England and London, running from 4pm on Thursday until 8pm on Saturday.

The UKHSA said it meant water-related incidents could increase, and warned of the risks from cold-water shock and drowning.

It follows a night of heavy downpours and frequent lightning strikes in parts of the country, mainly across the Midlands and in the north of England.

In recent days, young people have died in water-related incidents in Lincoln, Halifax, Rotherham, Warwickshire, Cheshire, Farnborough and Lancashire, along with a man in his 60s in Cornwall and a woman in her 70s in Wales.

Declan Sawyer, 15, died after getting into difficulties at Swanholme Lakes, Lincoln, on Sunday, while a 72-year-old woman died after being pulled from the water at West Angle Bay beach in Pembrokeshire, Wales, at about 3.15pm on the same day.

A 13-year-old boy, understood to be Reco Puttock, died after getting into difficulty at Leadbeater Dam, near Halifax, West Yorkshire, on Monday, and the body of a teenage girl was recovered from the water at Kingsbury Water Park, Warwickshire.

On the same day, a man in his 60s died following a cardiac arrest after he entered the sea at Tregirls Beach, near Padstow, to help two family members who were in difficulty.

The body of a teenager was recovered from the water at Rother Valley Country Park, Rotherham, in the early hours of Tuesday morning. Another body was found in the search for a teenage boy who went missing after he was last seen swimming at Hawley Lake, on the border of Hampshire and Surrey, on Tuesday afternoon.

A 12-year-old boy who died after getting into difficulties in the River Ribble, in Ribchester, Lancashire, on Tuesday was named as Junior Slater, from Clayton-le-Woods.

On Wednesday, Cheshire police said the body of a 17-year-old boy had been found after he went missing in Pickmere Lake, in Marston, Northwich.