You can spend days hiking through Glacier National Park. It has to be some of the most spectacular scenery in the world.
Glacier National Park can be visited year-round. However, the 'real' season is very short: June/July until August/September. June can only be recommended at lower elevations, as many areas are still snow covered. July and August are the pleasant peak months. September is still great in terms of weather and the crowds start to dissipate as well.
From late October until May/June you have to deal with snowfall or snow covered ground. June is 'rainy season' and most hiking trails are still snow covered well into June, on high elevations even until mid-July. July and August are the sunniest months. September is still great: Usually zero snowfall pleasant temperatures and less crowds (see below). New snow can be expected from mid October. However, heavier snowfall won't start before November.
The climate is often wet, windy and variable. Always be prepared for weather changes, even in the summer. Bring rain gear an dress in layers. Nights are much cooler. Also, be prepared for cooler temperatures at higher elevations. Popular areas like Logan Pass at higher elevations are usually 10-15°F (6-8°C) cooler. Bottom line: For a snow-free hiking adventure go between early July and mid-October. Please keep in mind that most services and lodges close between mid-September and end of September.
Avoiding Tourist Crowds
The park recently set new records for visitation. In the recent years the number of visitors increased significantly in the peak summer months. Resulting in overcrowded parking lots, a congested Going to the Sun Road and very busy popular areas.
Besides visiting the less interesting spots in peak season, there are three main options to avoid the crowds:
Visit in Fall:
September after the extremely busy Labor Day weekend is an excellent time: Less crowds, still snow free areas and pleasant temperatures. The GTTS (Going-to-the-Sun) Road is still open and most services are available until mid-September, some until the end of the month. The first half of September is already significantly less busy compared to July and August. However, not super quiet: Try to start your activities early (see below) and go mid-week if possible. It’s even quieter and still pleasant temperature wise from mid-September until mid-October. An excellent time for hiking. However, hotels, lodges and cabins in the park are closed by the end of September. Solution in October: Lodging outside the park in West Glacier Lodging (Glacier Highland) If you consider visiting in spring to avoid the crowds: It's not recommended for hiking adventures. The temperatures are often pleasant but the trails are snow covered well into June.
If you want to visit in the summer, getting out early is the best way to avoid crowds. Even on popular hiking trails like Highline or Grinnel Glacier Trail you won’t see many others during peak season if you start your hike at or before 8 a.m. One visitor reported that he started the hike to Grinnel Glacier in August 2017 at 7 a.m. and had the whole trail for himself. On the way back about 200 people passed. Your scenic drive on the GTTS should begin even earlier if possible. Usually it starts to get busy around 9 a.m on GTTS Road in the summer months.
Alternatively begin your activites late. Start hiking between 4 and 5 p.m. Although only shorter hikes are possible at that time, the trails are much quieter. The best short hikes include Hidden Lake Overlook at Logan Pass, Redrock Falls and Virigina Falls. Starting your scenic drive later is a great option as well: On the GTTS Road it’s beginning to thin out around 4 p.m. Tip: Have a late lunch or an early diner between 3 and 4 p.m., as it’s much easier to get a seat at that time Then start your scenic drive on GTTSR.
Highlight (Going-to-the-Sun Road)
Some parts of the GTTS Road are open all year. However, the fascinating portions on higher elevations are only open in summer and early fall. There is no set date, but the road is usually fully open from early July until mid-October. All depending on the weather and road conditions. More details: Going to the Sun Road - NPS