Wakefield Council are warning residents to avoid open water swimming this weekend, as temperatures are expected to reach 27 degrees.
The advice comes after a 12-year-old girl drowned in a river in Bury, Greater Manchester, on Thursday evening.
The Royal Society for the Prevention of Accidents is urging parents to speak to their children about the dangers of swimming in open water ahead of the hot weather this weekend.
Despite the warm weather, open water, such as rivers and lakes, can remain cold, and hidden dangers pose a risk to swimmers.
David Walker, leisure safety manager at RoSPA, said: “The main danger when swimming in open water is cold water shock, which affects your ability to breathe, overwhelms your ability to swim, and leads to drowning. It can affect even the strongest swimmers. Even though it’s hot outside, the water temperature is low enough to trigger cold water shock.
“Other dangers to look out for are currents, hidden objects and features such as weirs which drag people below the surface.
“The UK has some of the world’s best coastline and waterways, and we encourage people to go out and enjoy them this weekend and through the rest of the summer, but it’s important to be aware of the dangers.
"If you are planning to go swimming this weekend, choose a safe place such as a lido or lifeguarded beach. If you find yourself in trouble, remember to float first – fight your instinct to swim – control your breathing, then kick to the side.
“We urge parents to search online for facts about cold water shock, and have that conversation with children today before they go out over the weekend.”
Open water includes sites such as the ocean and inland waterways such as canals, rivers and lochs.
Hundreds of people die from cold shock each year while swimming in open water.
In 2007, a teenager died in Horbury after finding himself in difficulties in Horbury's Blue Lagoon.