The short answer
The freezing level is the altitude at which the air temperature is 0 °C. Air gets colder with height, roughly 6 °C for every 1,000 m, so on any given day there is a height above which the air is below freezing. Snow that forms high in a cloud stays snow as it falls until it drops below that height, then starts to melt.
Why it matters more than the temperature at the resort
A forecast of “2 °C” in the village tells you about one spot. The freezing level tells you about the whole mountain. If the freezing level is at 1,800 m, a resort whose village is at 1,300 m and whose top lift is at 2,500 m can expect rain low down and snow up high, with slush in between. If the freezing level drops to 1,000 m overnight, the same storm snows to the valley floor.
That is why every resort page on snowingplaces gives the freezing level alongside the day’s snowfall, and why each resort has two forecasts, one at the top lift and one in the village.
The snow line is lower than the freezing level
Snowflakes take time to melt. In heavy precipitation, falling snow cools the air it passes through, so snow usually reaches the ground a few hundred metres below the freezing level. Forecasters call the height where it turns to rain the snow line, and as a rule of thumb it sits 200 to 300 m below the freezing level, lower still when it is snowing hard.
What to look for
- A freezing level below the village means snow everywhere.
- A freezing level between the village and the top lift means it depends where you are. Head up.
- A freezing level above the top lift means rain, and rain on snow is the worst thing that can happen to a piste.
- A freezing level that is forecast to fall during a storm is good news: rain turns to snow as the storm goes on, and the top-up comes at the end.
Where our figure comes from
The freezing level on this site is the average of the GFS and ICON models; the ECMWF model does not publish it through our data source. It is a modelled figure for the free air, not a measurement, and in a valley in the morning the real air can be colder than the model says because cold air pools overnight.