Trips & expeditions
At what temperature does water boil at high altitude?
Lower than at home, because there is less air pressing down on the water. It boils at 100°C (212°F)212°F at sea level, at about 85°C (186°F)186°F at Barafu Camp on Kilimanjaro, 83°C (182°F)182°F at Everest Base Camp and about 72°C (161°F)161°F on the summit of Everest. As a rule of thumb, the boiling point drops by about one degree Celsius for every 300 m (about 1,000 ft)about 1,000 ft you climb, which is close to two degrees Fahrenheit.
Boiling points at the main camps
| Mountain | Camp | Height | Water boils at |
|---|---|---|---|
| Kilimanjaro | Shira Camp | 3,850 m12,631 ft | 88°C (190°F)190°F |
| Kilimanjaro | Barafu Camp | 4,640 m15,223 ft | 85°C (186°F)186°F |
| Kilimanjaro | Uhuru Peak | 5,895 m19,341 ft | 81°C (178°F)178°F |
| Aconcagua | Plaza de Mulas | 4,300 m14,108 ft | 86°C (188°F)188°F |
| Aconcagua | Nido de Cóndores | 5,560 m18,241 ft | 82°C (180°F)180°F |
| Aconcagua | Summit | 6,961 m22,838 ft | 78°C (172°F)172°F |
| Denali | Basin Camp | 4,330 m (14,200 ft)14,200 ft | 86°C (186°F)186°F |
| Denali | High Camp | 5,200 m (17,200 ft)17,200 ft | 83°C (181°F)181°F |
| Denali | Summit | 6,190 m (20,310 ft)20,310 ft | 79°C (175°F)175°F |
| Everest | Base Camp (Nepal) | 5,360 m17,585 ft | 83°C (182°F)182°F |
| Everest | Camp 2 / Advanced Base Camp | 6,400 m20,997 ft | 80°C (176°F)176°F |
| Everest | South Col | 7,925 m26,001 ft | 75°C (167°F)167°F |
| Everest | Summit | 8,849 m29,032 ft | 72°C (161°F)161°F |
The pressures come from John West's model atmosphere for Everest's latitude (1996) and, for Denali, from the measured summit pressure in the climbing season; the boiling points from the standard formula for water. Weather moves them by about a degree. The camp heights are the ones in our guides.
Does the freezing point change too?
No. Ice melts and water freezes at 0°C (32°F)32°F at any height on earth. Boiling turns water into vapour that takes up about 1,600 times the space, so the pressure of the air matters a great deal. Freezing changes the volume by only about 9 percent, and halving the air pressure moves the melting point by less than a hundredth of a degree.
Does latitude make a difference?
Yes, a little. The air is warmer and deeper over the tropics than near the poles, so at the same height the pressure is lower the further north or south you are. Denali, at 63°N, has a summit pressure in summer that you would meet at about 6,550 m21,490 ft in the Himalaya, and its water boils about one degree lower than it would at the same height near Everest. Cold weather lowers the pressure further: in January the water on Denali's summit would boil at about 77.5°C172°F.
Does the air temperature change the boiling point?
Only through the pressure. A cold morning does not change the temperature at which your pot boils, but a cold column of air holds less pressure high up, which is why winter and high latitudes lower it. What cold air does change is how long the pot takes, because the pot loses heat to the air and the snow has to be warmed before it melts.
Is water that boils at 83°C181°F safe to drink?
Yes, if you boil it for longer. Heat kills germs over time. The US Centers for Disease Control and Prevention advises a rolling boil of one minute, or three minutes above 2,000 m (6,500 ft)6,500 ft. On Kilimanjaro your crew treats the drinking water; see Is the water safe to drink on Kilimanjaro?
What do the big expedition kitchens use?
On Kilimanjaro, where the national park banned firewood, the crews cook on gas cylinders carried up by porters. Everest's base-camp kitchens cook on gas from large cylinders and use pressure cookers, which raise the boiling point back above 100°C212°F (about 112°C234°F at Everest Base Camp), so rice and lentils cook properly. On Aconcagua the service companies at Plaza de Mulas and Plaza Argentina run kitchens at base camp. On Denali there are no camp staff, and every team cooks for itself on white-gas stoves.