Real-time 0 °C isotherm and rain-snow limit
The 0 °C isotherm indicates the altitude where free-air temperature reaches freezing. During steady precipitation, snowflakes typically fall 200 to 400 meters below this isotherm.
Instant Weather France › Mountain Weather
The Mountain Weather observatory supports hikers, mountaineers and skiers across the seven major French mountain ranges: Northern Alps, Southern Alps, Pyrenees, Massif Central, Vosges, Jura and Corsica. Check conditions by elevation band from valley floors to the highest peaks.
The 0 °C isotherm indicates the altitude where free-air temperature reaches freezing. During steady precipitation, snowflakes typically fall 200 to 400 meters below this isotherm.
For each resort and summit, check snow depth at the base and top of slopes, 24-hour fresh snowfall totals and snowpack quality.
Strong winds on ridges transport large volumes of snow and form wind slabs on lee slopes. Always verify the avalanche danger scale (1 to 5) before any backcountry outing.
In a standard atmosphere, temperature decreases by an average of 0.65 °C per 100 meters of elevation gain, except during winter temperature inversions.
Level 3 (considerable risk) means avalanches can be triggered by a single skier or hiker on many steep slopes; solid snow-safety experience is essential.
Ultraviolet radiation increases by about 10% every 1,000 meters of elevation, and fresh snow reflects up to 85% of UV rays.