Plan the day around the heat, not the itinerary. Above 90 °F the safe working window is roughly 6–10 a.m. and after 5 p.m.; the middle of the day belongs to shade and water. Camping in heat is not dangerous if you move the effort to the edges of the day and treat the tent as a shaded box rather than a bedroom until the sun drops.
Heat index: the number that matters
The heat index combines temperature and humidity into what it feels like. Humidity is the multiplier because sweat only cools you when it evaporates.
| Temperature | 40% humidity | 60% humidity | 80% humidity |
|---|---|---|---|
| 90 °F | 91 | 96 | 105 |
| 95 °F | 96 | 104 | 115 |
| 100 °F | 102 | 112 | 124 |
Above a heat index of 103 °F, cut all strenuous activity. Above 115 °F, treat it as an emergency: shade, water, no hiking.
Water: rate, not total
| Condition | Per person per day | Notes |
|---|---|---|
| 80–90 °F, light activity | 3–4 L | 1 gal ≈ 3.8 L |
| 90–100 °F, hiking | 5–7 L | Add electrolytes if sweating heavily |
| Above 100 °F | 7–10 L | Plus a reserve for cooking |
| Children | 60–70% of adult rate | Smaller body, faster dehydration |
Drink before thirst. Thirst appears at roughly 1–2% body-water loss, and performance drops before that. A practical check: urine should be pale straw, not dark.
Caffeine and alcohol both increase water loss; keep them for the evening, and drink water alongside.
Shade strategy
| Option | Temperature drop | Weight |
|---|---|---|
| Natural tree shade | 8–12 °F | 0 |
| Tarp / canopy over the tent | 8–15 °F | 2–5 lb |
| Reflective fly | 5–10 °F | Included with some tents |
| No shade, tent closed | 0 (greenhouse) | 0 |
The single most effective move is a tarp over the tent: it blocks direct sun and lets air move underneath. A closed tent in full sun becomes 15–20 °F hotter than outside air by mid-morning.
Pitch so the tent’s narrow end faces the morning sun, and open both doors during the day when you are away.
Cooling the tent at night
- Choose a mesh-heavy tent or sleep under a bug net with no fly.
- Pitch facing the evening breeze, not in a hollow where air pools.
- Sleep on a cot or a raised pad; the ground stores the day’s heat.
- Use a quilt instead of a bag above 65 °F.
- A damp cloth on the neck cools faster than a fan.
- Battery fan with 8+ hours of runtime is worth its weight in August.
Activity timing
| Window | Temperature | What to do |
|---|---|---|
| 5–9 a.m. | Coolest | Hike, move camp, long distance |
| 9–11 a.m. | Rising | Short moves, water resupply |
| 11 a.m.–4 p.m. | Peak | Shade, sleep, read, swim |
| 4–7 p.m. | Falling | Cook, explore, set camp |
| After dark | Radiation cooling | Sleep with vents open |
This is the siesta pattern, and it is not laziness — it is the only schedule that keeps heat stress low.
Heat illness: signs and response
| Stage | Signs | Action |
|---|---|---|
| Heat cramps | Muscle cramps, heavy sweating | Stop, shade, electrolytes |
| Heat exhaustion | Headache, nausea, dizziness, cool clammy skin | Shade, lie down, cool neck and wrists, fluids over 30 min |
| Heat stroke | Confusion, no sweating, hot skin, collapse | Emergency: cool aggressively, call for help, evacuate |
Heat stroke is a medical emergency. Confusion plus a temperature above 104 °F means evacuate, not rest.
Keeping water drinkable
Warm water is the reason people stop drinking. Three cheap fixes:
- Store bottles in the shade, wrapped in a wet towel; evaporation keeps them 10–15 °F cooler.
- Bury bottles 6 in deep in shade — soil is cooler than air all afternoon.
- Freeze one bottle overnight and use it as the day’s cold reserve; it also cools the food bag.
A 2 L bladder in a pack hose warms to air temperature within an hour. Insulated sleeves are worth the 3 oz.
Camp setup in heat
- Cook in the evening and morning; a stove adds heat to the site.
- Keep food in a cooler with block ice, not cubed — it lasts 2–3 days longer.
- Set the tent up in shade if you plan to be back before sunset.
- Store water in the shade; hot water tastes bad and warms you.
- Wear loose, light-coloured long sleeves; they block sun better than skin.
Where to go next
For humidity and condensation in the tent, see the storms guide; for layering in cold, the cold and moisture guide; for choosing a month, the best season guide. For heat illness response thresholds, see the safety guide.
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