Winter season runs from late November through early April. The best snow is usually February through March, when the storms come heavy and the daylight hours start to lengthen. Holiday weeks (Christmas–New Year and the third week of February) are expensive and busy; January and early March are the sweet spot for value and crowds.
Summer season runs from mid-June (once the high trails clear) through late September. July is reliably warm; August brings afternoon thunderstorms over the peaks; September turns the aspen groves around the Maroon Bells gold for about three weeks in the second half of the month — book early for that window.
Shoulder seasons (April–May and October–November) are quiet, with limited dining and lift operations. The off-season is real here.