Park City has three distinct high seasons. January is peak Sundance time — the film festival runs for ten days usually starting the third Thursday of the month. Accommodation is extremely tight and expensive; book six months ahead if you want to attend. December through March is the ski season, with Christmas–New Year and Presidents' Week being the busiest and most expensive periods. Summer (June–September) is pleasant for hiking and biking with much lower prices and crowds.
The shoulder months of April–May and October–November are the quietest: lifts are closed, the festival crowd is gone, and the town is genuinely peaceful. Snow can fall at any time from October through May at this elevation (7,000 feet).