This effect is worse for higher temperatures where it can increase the effective ambient temperature by as much as 10 degrees. Air movement over the body enhances the ability to lose heat by convection and evaporation. Movement is generated both by the runners speed and by any prevailing wind. These can combine to lower the effective temperature by as much as 8 or 9 degrees while increasing evaporation and fluid loss. Running downwind cancels out this cooling effect.
Direct sunlight adds heat to the body by radiation.
The effective temperature increase can be as much as 8 or 9 degrees. Running unwisely under environmental heat stress may lead to a variety of heat illnesses which can be life threatening. If these signs occur, stop running and start the appropriate treatment. They could be symptoms of any of the major heat illnesses described below. Heat Cramps Salts can be lost in the sweat while running in the heat.