Peak season is June to September, with beautiful, warm days and mild nights. Late summer can get hot and dry, with temperatures that heat up to 100—though things cool off quickly in the higher altitudes of the surrounding mountains. A float down Boulder Creek in an inflatable tube also does the trick. Summer evenings are mild, sometimes even requiring a light jacket.
Spring shoulder season in Boulder (or “mud season,” as locals know it) runs April to May, with lower hotel rates and pleasant weather. Snowmelt causes the streams to rush during this time, making the kayaking either great or suicidal, depending on your point of view. Trails are often muddy and the high mountains still have snow, making some high-altitude hiking impossible. May’s graduation weekend jacks up hotel rates and makes traffic unbearable.
In October through December, fly-fishermen try to find quiet spots on the area’s prized trout streams, and mountaineers shoot for the summits of surrounding 14,000-foot peaks. Autumn brings the return of the student population to CU-Boulder, so the area around “The Hill” (across the street from the university) is best avoided, especially during the Buffaloes’ home football games. November can still bring on sunny and warm days in the 50s.
Off-season in Boulder runs from January through March. This is when the Colorado traffic shifts to the mountain resorts for skiing, snowboarding, and snowmobiling. Although snowfall is expected, winters can be mild and less snowy than on the East Coast, and the light, powdery fluff melts off quickly in most months. February and March see high winds and temperatures cold enough to keep snow around for a few weeks.
The big snows come to the surrounding mountains, where great skiing is about an hour-and-a-half west along I-70. For relatively crowd-free skiing, many locals and visitors turn their eyes to Eldora Mountain Resort, just 30 minutes from downtown Boulder. Winter is also celebrated in Boulder with snowshoeing and cross-country skiing on nearby trails.
Boulder’s most popular events include the Bolder-Boulder 10K race; summer’s Colorado Shakespeare Festival; and Memorial Day’s Boulder Creek Festival, when artists, food tents, and bluegrass musicians fill the park along Boulder Creek.