To ensure the safety of participants, World Athletics has a heat rule which can be applied when temperatures get too high.

The Wet Bulb Globe Temperature (WBGT) scale is used to determine whether the heat rule should be enforced.

The WBGT measures heat stress in direct sunlight, which involves observing temperature, humidity, wind speed, sun angle, and cloud cover.

For athletics events, a warning is issued when temperatures reach 25C, and severe warnings are issued when temperatures reach 28C.

Competing at temperatures of 30C and above are classed as dangerous.

To reduce the risk of heat illnesses, athletics competitions are often scheduled during cooler mornings or evenings.

Health advice suggests distance races should take place below 18C.

World Athletics president Sebastian Coe said there will be “heat challenges” at the championships in Tokyo.

He added the battle against climate change had fallen on sports leaders after inaction from governments.

“Governments have not stepped up to the plate and sport is going to have to take some unilateral judgments and decisions here,” said Coe.

“And we have reflected in the past, if we are committed to athlete welfare, then we should probably be openly committed to that.”