WILTSHIRE families are being urged to think twice before heading to rivers and lakes to cool off this week, as fire crews warn that a quick dip in open water can turn deadly in seconds.

With temperatures climbing and a red heat alert in place, Dorset and Wiltshire Fire and Rescue Service has issued a stark reminder that rivers, lakes and the sea can remain dangerously cold even on the hottest days, creating a serious risk of cold-water shock.

The service said the sudden drop in temperature can trigger an involuntary gasp response, make breathing difficult and cause panic, leaving even confident swimmers struggling to stay afloat.

Firefighters are urging anyone who gets into difficulty in the water to fight the instinct to thrash around and instead float on their back until the effects pass, before calling for help or swimming to safety.

If someone else is in trouble, the advice is clear: call 999 immediately. At the coast, ask for the coastguard; inland, ask for the fire service.

People are also being told never to enter the water to try to rescue someone themselves and, instead, throw them something that floats and encourage them to lie back and float.

Wiltshire Council has now joined the warning, urging parents and carers to speak to teenagers who may be tempted to head for rivers, lakes or quarries as the heat rises.

The council said open water can contain hidden hazards, strong currents and sudden drops, even where it appears calm from the bank.

Young people are being encouraged to use supervised swimming pools where possible and to remember the “float to live” advice if they get into trouble.

Parents are also being asked to make sure children know how to describe their location in an emergency, including by using the what3words app if needed.

Officials hope the warning will prevent avoidable tragedies as Wiltshire braces for some of the hottest weather of the year.