Forecasts for the most-visited summits and high country. Conditions up top routinely run 15-25°F colder than the trailhead, with wind that can triple — check before you climb.
Data sources
Summit conditions are serious business
Summit temperatures are estimated from the valley forecast using the standard lapse rate (−6.5°C per 1,000 m); wind chill on an exposed ridge will feel far colder, and wind speeds are typically two to three times stronger than in the glen. Always check an official mountain forecast before heading up, carry a map and compass, and turn back if the cloud comes down.