How reliable are ski resort opening dates?

An opening date is an announcement. Snow is weather. Across 53 destinations and 10 seasons the two agree far less often than a season calendar suggests: 13 of the 53 have not had 30 cm of natural snow on the ground in their own opening week in a single one of the last 10 seasons, and only 6 have managed it in all 10.

This page is the answer to the general question rather than a ranking. If you want the ranking, it is the index itself.

The place matters more than the year

The best year in the record put 26 of 53 destinations on real snow at opening. The worst put 18. That is a spread of 8 destinations across a decade of weather, and it never once collapsed to a season where nothing worked or rose to one where everything did. Individual destinations, meanwhile, range across the full width of the scale from 13 sitting at zero to 6 at ten.

The practical reading: choosing the right mountain for the date is worth far more than choosing the right year. A destination with a ten-in-ten record is not being rescued by a good winter, and one at zero is not being punished by bad luck.

What an announced date can and cannot tell you

It tells you when the lifts intend to turn. It carries real information: resorts do not pick dates at random, and a mountain that has opened in the same week for thirty years knows something about its own climate. What it cannot tell you is whether the snow will be there, because the date is fixed months ahead and the weather is not, and because a resort with enough snowmaking can honour a date the sky has not earned.

This index separates those two things on purpose. It scores the week, not the operation. A low score means the atmosphere did not deliver in that week; the scope page sets out exactly what is left out and why.

The limits of the number

Three, stated plainly. First, this is a reanalysis, not a measurement: a model can be too smooth over complex terrain and can miss a local storm. Second, each destination is read through one grid cell whose elevation is the average of the terrain inside it, so a score is a comparison between places rather than a depth you would find under your skis. Third, the opening windows are traditional, resolved from each destination's own published season by a fixed table applied identically to all 53, and resorts move their dates for snow, staffing, events and holiday calendars. The full method, including how the windows are resolved, is on the index page.