High-altitude cooking is cooking done at altitudes that are considerably higher than sea level. At elevated altitudes, any cooking that involves boiling or steaming generally requires compensation for lower temperatures because the boiling point of water is lower at higher altitudes due to the decreased atmospheric pressure. The effect starts to become relevant at altitudes above approximately 2,000 feet (610 m). Means of compensation include extending cooking times or using a pressure cooker to provide higher pressure inside the cooking vessel and hence higher temperatures.

does altitude change the boiling point of water?
yes