Heat illness develops progressively and the early stages are easy to dismiss as ordinary tiredness. This guide covers prevention and recognition. Treatment beyond immediate cooling and getting help belongs to medical professionals, and anyone showing serious signs needs emergency care rather than field management.
- 1
Understand what makes heat dangerous
Your body sheds heat mainly by sweating, and sweating only works if the sweat evaporates. High humidity blocks that, which is why a humid 85°F day is more dangerous than a dry 95°F one. Add direct sun, exertion, and a lack of airflow and heat accumulates faster than you can shed it.
- 2
Plan around the heat rather than through it
Start early and get the exposed climbing done before mid-morning. Rest in shade during the hottest hours instead of pushing through. Reduce your planned mileage on hot days rather than treating the schedule as fixed — heat makes the same distance substantially harder.
- 3
Drink and salt together
Sweating loses both water and sodium. Drinking large volumes of plain water while sweating heavily can dilute blood sodium and produce symptoms that resemble dehydration. Eat salty food or use an electrolyte product alongside fluid on long hot days.
Electrolytes explainedWhat sodium does and when you need itRead Guide → - 4
Dress for evaporation, not for less fabric
A light-coloured loose long-sleeve sun shirt is usually cooler than bare skin in direct sun, because it blocks radiant heat while letting sweat evaporate. Wet a hat or a neck gaiter at water crossings — evaporative cooling at the head and neck is noticeably effective.
Sun protectionClothing that keeps you coolerRead Guide → - 5
Recognise the early signs and act on them
Heavy sweating with cramping, unusual fatigue, headache, dizziness, nausea, or clammy pale skin are signals to stop, get into shade, cool down, and drink with salt. Acting at this stage generally resolves it. Continuing to walk is what allows it to progress.
- 6
Know what is an emergency
Confusion, altered behaviour, loss of coordination, fainting, a very high body temperature, or skin that is hot and no longer sweating are medical emergencies. Cool the person as rapidly as possible, get help immediately, and treat this as urgent — do not wait to see whether it improves.
Calling for helpEmergency contact without phone coverageRead Guide →
Risk Factors
| Factor | Effect |
|---|---|
| High humidity | Blocks evaporative cooling |
| Direct sun and no shade | Adds radiant heat load |
| Sustained exertion | Generates internal heat |
| Inadequate fluid or salt | Reduces sweating capacity |
| No acclimatization | First hot days of the season are riskiest |
| Certain medications and conditions | Can affect heat tolerance — ask a doctor |