On Everest, water boils at about 70 degrees.
Water boils when its vapour pressure matches the air pressure. At sea level that happens at 100 °C. The higher you climb, the thinner the air and the sooner it boils: around 93 °C at 2,000 metres, about 70 °C on Everest's summit at 8,849 metres. That's why cooking takes longer in the mountains, not shorter.
Useful: A pressure cooker flips the principle: more pressure, water boils only at about 120 °C, food cooks faster.
Source: en.wikipedia.org