As temperatures soar across the Northern Hemisphere, a free tool lets anyone, anywhere check how dangerous the heat really is for their sport and decide whether it is safe to play.

Most people who play sport judge heat by the temperature, or simply by how it feels. But the real danger depends on much more than that. Humidity, the sun, and how hard you are working all affect how much heat your body has to shed, which is why two days at the same temperature can carry very different risks.

The Sports Heat Tool, developed at the University of Sydney, now calculates that risk for anyone, providing sport-specific guidance on heat exposure and a clear answer to a question that millions of people ask each summer: is it too hot to play?

The interactive online tool, downloadable for free from the Apple App Store and online, is designed to help people monitor their heat risk while participating in more than 33 sports and guide safe participation during hot conditions.

From soccer and softball, to canoeing and cycling, users around the world can search their location, check their heat risk, and discover a sport-specific risk profile based on the activity they are doing.

Professor Ollie Jay, Director of the Heat and Health Research Centre at the University of Sydney, who helped develop the tool, said the gap between elite and community sport is stark.

At the elite level there are doctors, cooling stations, and someone whose job it is to call it off when it gets dangerous,” said Professor Jay. 

“A local club has a coach, a hot afternoon, and a judgement call. We have taken the science that the professionals rely on and put it in everyone’s pocket for free. Your body follows the same rules whether you are playing at the FIFA World Cup or a Sunday league.”

How to check your heat risk

Users can enter their location and choose their sport, then the app returns a sport heat-risk score for the hours and days ahead, ranging from low (1.0) through to extreme (5.0), alongside practical steps to bring the risk down.

“It models how a real body exchanges heat with its surroundings, rather than relying on older indices designed decades ago for narrow conditions. It accounts for the temperature, the humidity, the sun and your own exertion, so the risk it shows is the risk you are genuinely facing,” said Dr Federico Tartarini, from the Heat and Health Research Centre and the Sydney School of Architecture, Design and Planning, who co-developed the tool.

A version tailored to children and adolescents, whose bodies manage heat differently to adults will be launched later this year.