How SkiWhen predicts ski crowds

SkiWhen gives every mountain a crowd score from 0 to 100 for each of the next seven days, then labels it Quiet, Busy or Packed. Here's what goes in.

1. The day of the week

The biggest single factor. Saturdays are the busiest day almost everywhere, Sundays a little less, Fridays pick up, and Tuesdays and Wednesdays are the quietest.

2. Holidays

Thanksgiving, the stretch from Christmas to New Year's, MLK weekend and Presidents' Day weekend (Family Day in BC, Alberta and Ontario) add a large bump. SkiWhen applies US holidays to US mountains and Canadian holidays to Canadian ones.

3. School breaks

When a state or province is on break, its mountains get busy on weekdays too. Breaks are matched to each mountain's own state or province, which is why Vermont gets slammed in February vacation week while Colorado doesn't.

4. Snow and weather

Forecasts come from the National Weather Service (US) and Open-Meteo (Canada), adjusted to mid-mountain elevation. A big powder day pulls people up; a sunny day after a storm does too; rain, strong wind and bitter cold keep people home.

5. The mountain itself

Some mountains are simply busier: close to a big city, on a big pass, or famous. Each one has a popularity factor that we tune as we learn.

What SkiWhen can't know (yet)

Lift breakdowns, parking changes, special events and one-off deals. That's why every forecast is an estimate. We're adding real check-ins from skiers to keep improving it.