Adjust expectations, exposure, clothing and hydration when heat changes the demands of race day.
Treat heat as part of the course
Check the forecast and organiser guidance. Heat and humidity can make a familiar pace substantially harder, so plan to reduce effort and use shade or cooling opportunities.
Wear light, comfortable clothing and avoid chasing a cool-weather goal at any cost.
Practise, do not improvise
Use training to test drinking, carrying fluid and taking aid-station cups. Needs vary, and both too little and excessive fluid can be harmful; runners with medical conditions should seek individual advice.
Arrive hydrated through normal drinking rather than forcing large volumes at once.
Recognise heat illness
Stop, cool down and seek help for dizziness, weakness, nausea, confusion or fainting. Confusion, collapse or very hot skin can signal an emergency requiring immediate medical assistance.