When to actually go
The Austrian Alps ski season generally runs late November through April, but elevation changes that window meaningfully between these three resorts.
Highlighted months are the reliable core of the season across all three resorts; edge months depend heavily on elevation and snowfall that year.
Elevation decides your snow risk
St. Anton's top station at 2,811m and Innsbruck's Stubai Glacier at over 3,000m both hold snow reliably deep into the season and, in the Stubai's case, effectively year-round at the glacier itself. Kitzbühel's lower elevation range (800–2,000m) makes it more exposed to a thin or late-arriving season at the start and end of winter — it's not a reason to avoid Kitzbühel in a normal season, but it's worth checking snow reports before an early-December or late-March trip there specifically.
Crowds and pricing follow the calendar, not the snow
Christmas and New Year, and the February school-holiday period across several European countries, are the busiest and most expensive weeks at all three resorts regardless of conditions. January outside the holiday weeks and early-to-mid March tend to offer the best combination of reliable snow and thinner crowds.