Summer, autumn, and winter are the best times to visit the Northern Rockies. The days are sunny, the nights are clear, and humidity is low. A popular song once romanticized "Springtime in the Rockies," but that season -- or what most people think of as springtime -- lasts about 2 days in early June. The rest of the spring season is likely to be chilly with snow or rain; most of the annual moisture in these states falls during March and April.
Summer is the best season to visit for hiking, fishing, camping, and wildlife-watching. It will be warm during the day and cool at night. In Montana, average highs in July run from 79°F (25°C) in West Yellowstone to 89°F (32°C) in Miles City; lows at night range from 38°F (3°C) to 60°F (16°C).
Fall brings spectacularly clear days; cool, clear nights; and calm winds up until late October, when things get iffy again. Weather is changeable, however, and snow is possible -- even likely -- in the high country, so don't try an extended backpacking trip unless you are experienced and well prepared. Actually, this is a requirement year-round; you can get caught in mountain snowstorms in July and August.
Winter is a glorious season here, though it can be very cold. Lows in Havre, Butte, West Yellowstone, and Jackson average single digits Fahrenheit (about -15°C) in January. And it can be very windy in some parts of these states, especially on the plains. But the air is crystalline, the snow is powdery, and the skiing is fantastic. If you drive around Montana and Wyoming in the winter, always carry sleeping bags, extra food, flashlights, and other safety gear. You need to be prepared to survive if your car breaks down or you get stuck in a blizzard or snow squall. Every resident has a horror story about being caught outside unprepared. Only the north entrance at Yellowstone National Park is open to automobiles in the winter. Lodging is available in the park only at Mammoth and Old Faithful. Ski resort towns, such as Jackson and Kalispell, stay lively all winter, but summer tourist towns, such as Cody, are quiet.
Weather & Road Conditions -- For up-to-date information on current weather, contact the National Weather Service at tel. 406/449-5204 in Montana, tel. 307/772-2468 in Wyoming, or online at www.wrh.noaa.gov. For statewide road conditions, contact the Montana Department of Transportation (tel. 800/226-7623, or 511 in Montana; www.mdt.mt.gov).
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.