Even though the park is open year-round, Trail Ridge Road, the main east-west thoroughfare, is always closed in winter. Assume that you will not be able to drive clear across the park from mid-October until Memorial Day -- even into June and again in September, snow can close the road for hours or even a day or more. That's not to say that travelers can't enjoy the park in winter. All park entrances are open, trails accommodate snowshoers and cross-country skiers, and roads to a number of good view points and trail heads are plowed. Those with the proper skills and equipment can cross-country ski into the high country, although they need to be aware of storm and avalanche dangers. Always check with rangers before setting out.
Weather is a key factor that will affect your trip to the park in any season. In summer, temperatures typically climb into the 70s (20s Celsius) during the day and drop into the 40s (single digits Celsius) at night, but because of the park's high elevation and range of elevations, temperatures vary greatly. The higher into the mountains you go, the cooler it gets. Rangers say that for every 1,000 feet in elevation gain, the climate changes the equivalent of traveling 600 miles north. The tree line in the park -- the elevation at which trees can no longer grow -- varies but is at about 11,500 feet.
Winters usually see high temperatures in the 20s and 30s (below 0 Celsius) and lows from -10°F (-23°C) to 20°F (-7°C). Spring and fall temperatures can vary greatly, from pleasantly warm to bitterly cold and snowy. For this reason, spring and fall are when you need to be flexible and ready to adjust your itinerary to suit current conditions. Particularly at higher elevations, wind-chill factors can be extreme. Hypothermia can be a problem at any time, even in summer, when afternoon thunderstorms sometimes cause temperatures to drop dramatically and suddenly.
The elk rutting season in September and October brings hundreds of elk to the lower elevations, where you can often hear the bulls bugle and watch them trying to keep other bulls away from their females.
Avoiding the Crowds
The park is fully accessible for only half the year, so few of the park's almost three million visitors come in the off season. The busiest time is from mid-June through mid-August -- essentially during school vacation -- so just before or just after that period is best. But winter is gaining in popularity, too, because it is the quietest time. You won't be able to drive the entire Trail Ridge Road, and the park can be bitterly cold, but it is also beautiful. Regardless of when you visit, the best way to avoid crowds is to head out on a trail.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.