Mountain Pass Closures and Opening Dates

Current gate status is published by the highway department or park that runs the road, and every page here links that agency’s own live page. A gate goes up in an afternoon and comes down two days later, decided by the crew looking at the road, so the agency page on the day is the one to plan on. What these pages give you is the shape of a normal season, the measured snow depth at the pass, and the phone number for the recorded line.

There is no single answer and the spread is the interesting part. Across the 19 roads on this site with at least 5 published seasons, the median closing runs from October 15 on Old Fall River Road to December 16 on June Lake Loop. The California Sierra gates are the surprise: Sonora Pass has a median closing of December 16, weeks later than most people assume, because a dry autumn on the east side of the Sierra will hold a gate open into December. Elevation is a weaker predictor than aspect and latitude.

They are different roads with different answers and conflating them is the commonest mistake in this subject. 36 of the 70 passes listed here shut entirely behind a gate for the winter, so the answer in January is that there is no road. The other 34 stay open all winter and what varies is whether you need chains or traction tyres to use them today. Snoqualmie Pass, Wolf Creek Pass and Teton Pass are all in that second group and are all regularly described as seasonal closures. They are not. What closes them is a storm or an avalanche control shot, and it lasts hours rather than months.

Chinook Pass in Washington, which has a published opening and closing for every year since 1935, 91 seasons without a gap. Going-to-the-Sun Road over Logan Pass in Glacier National Park is close behind at 90 seasons from 1933, and it is the more useful record because the park attaches a footnote to each unusual year explaining what happened. Trail Ridge Road in Colorado runs from 1932 but the published table stops at 2009, which the Colorado page states.

Because six states have either a published record of their gate dates or a live pass feed a browser can read, and the other forty four have neither. That is not a claim that the other states have no mountain passes. Colorado, Wyoming, Montana, Utah, Nevada, Oregon, Idaho and Alaska all have real seasonal gates, and their highway departments publish road conditions through keyed systems or not in machine readable form at all. Six of those eight have a page here, because a published date record from a national park or from the text of an agency press release is enough on its own. Nevada and Oregon have neither, and current status for their passes is on each highway department's own traveller information site.

No, and there will never be one here. A median from fifty years of a park’s own record is arithmetic on published numbers and is labelled as such. A predicted date for this year would be a model of a plowing operation through avalanche terrain, and people drive six hours on answers like that. Lassen Volcanic National Park says it about its own road: "The park does not have an established date for the full opening of the park road." If the park will not name a date for its own highway, a website has no business naming one for it.

Chain control is a graduated restriction a state applies to a road it is keeping open. California publishes it as a code on each of more than a thousand named points on its highways and refreshes it about once a minute, which is why the California page can show you a live reading. A restriction level tells you what equipment you need to proceed. A closure tells you there is no proceeding. The two get mixed up constantly because both arrive as red text on a highway department map, and because the same storm often produces one and then the other on the same road within a few hours.

From SNOTEL, the automated snowpack network the USDA Natural Resources Conservation Service runs across the mountain West. Each site reports the depth of snow on the ground from a sonic ranger and the water contained in that snow from a fluid pillow under the pack. Both are physical measurements rather than model output, which is why they appear here at all. A SNOTEL site is a forest clearing, not a roadway: it is never plowed, it can sit hundreds of feet above or below the pavement, and a deep reading there says nothing about whether a plow has been through. Every reading on this site names its station and that station’s elevation so you can judge how much it is worth.