The boiling point of water is lower at higher altitudes due to the decreased atmospheric pressure. High-altitude cooking requires a compensation for lower temperatures for any cooking that involves boiling or steaming. This effect starts to become relevant at altitudes above 2,000 feet (610 m). Means of compensation include boiling/steaming for longer times or using a pressure cooker to provide higher pressure inside the cooking vessel, and hence higher temperature.

does water boil at different temperatures at different altitudes?
yes