Explore the cold, windy, fast-changing weather found high above treeline.
High elevation lowers temperature and air pressure while steep terrain creates dramatic differences over short distances.
Rising air expands and cools.
Learn MorePressure and oxygen decline uphill.
Learn MoreFrozen water stores winter precipitation.
Learn MoreTerrain redirects and accelerates airflow.
Learn MoreSlope and direction create microclimates.
Learn MoreWarming alters snow, ice, and habitats.
Learn MoreAir pressure decreases with height. As rising air expands in lower pressure, it cools, so mountaintops are generally colder than nearby valleys. This temperature pattern creates elevation zones and can turn valley rain into snow higher on the same slope.
High-altitude air contains fewer oxygen molecules in each breath. People arriving quickly may experience headache or fatigue while their bodies adjust. Lower pressure also changes boiling temperatures and weather behavior, while stronger ultraviolet radiation makes sun protection especially important.
Mountain snowpack stores water through winter and releases it during spring and summer. Wind redistributes snow into deep drifts and bare ridges. Temperature layers within a snowpack can create weak zones, so storms, warming, or extra weight may trigger avalanches.
Ridges force air upward and funnel it through passes. Slopes heat by day and cool after sunset, producing regular upslope and downslope breezes. Powerful descending winds can warm and dry rapidly, melt snow, and raise wildfire danger on the sheltered side of a range.
A sunny south-facing slope in the Northern Hemisphere may be much warmer and drier than a shaded north-facing slope. Valleys can trap cold air, while peaks enter clouds. These microclimates determine where snow lingers and where particular plants and animals live.
Many mountain regions are losing glaciers and experiencing earlier snowmelt. Water may arrive before farms and ecosystems need it most, and species adapted to cold are pushed higher. Monitoring snow, temperature, and streamflow helps communities plan for floods, drought, and changing hazards.