Montana and Idaho Climate and Weather

Climate & Weather

The summer season of the Continental Divide is a short one, generally lasting from early June to mid-September. The trail’s accessibility is mostly a function of the amount of snow that fell the preceding winter. Snow continues to fall in May and June. Here’s a generalized look at the Montana/Idaho CDT from south to north: From the Island Park area near Yellowstone, through the Henrys Lake Mountains and most of the Centennials, snowfall is heavy. You’ll find snow on trails do not melt until July 4th or later. From Monida Pass to Goldstone Pass you’ll find lesser amounts of snow, so this section can be accessed by mid-June. From Goldstone Pass to Big Hole Pass the trail receives heavy snowfall and snow lingers until mid-July, and sometimes later. Big Hole Pass to Schultz Saddle may open by late June, but some passes north of there in the Anaconda-Pintler Wilderness do not clear until mid-July, and sometimes later. East of the Anaconda-Pintler Wilderness, the CDT curves like a scythe as it goes around Butte, Montana, mostly through lower elevation mountain ranges. This section can be hiked by mid-June if you don’t mind crossing infrequent snowfields. Most of the area north of Lowland Campground, in the Boulder Mountains, is clear of snow by late June all the way to Black Mountain below Stemple Pass. The exception is the CDT near the ghost town of Leadville and near Thunderbolt Mountain. They will not be clear of snow until early to mid-July. From Black Mountain northward, including Rogers Pass, the Scapegoat Wilderness, the Bob Marshall Wilderness, and Glacier National Park, you can encounter snow any time of the year.

Most trails are clear by mid-July. However, in Glacier National Park one can traverse old snowfields in September. You will need an ice axe and the ability to self-arrest if you hike through Glacier National Park in June. Gentler segments, with good road access, may be traversed with snowshoes or backcountry skis from November to March or April. Avalanche dangers are extreme along most of the CDT, so winter enthusiasts may want to limit their excursions to officially designated cross-country ski trails.

Usually high or low snowfall will affect trail conditions and the dates that trails melt out. The Forest Service monitors the snow pack, so a quick call to the right district can help you plan. Be prepared for snow and freezing cold, even in the height of summer. Nighttime temperatures during the summer routinely dip into the low 30s, so make sure your sleeping bag can handle freezing conditions.