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When is Winter?
The first time you look at a California road map you might be quite surprised to see “winter closure” on several of the Sierra Nevada mountain pass roads. If you are from another part of the country—or the world—you might assume that “winter” means winter on the calendar. The time from the winter solstice until the spring equinox. We won’t hold that against you. And we hope the mountains won’t either. Sierra road conditions can change suddenly.
We really hope the first time you learn about our winter Sierra mountain pass road closures isn’t on your vacation of a lifetime when you had planned to drive your rental car through Yosemite National Park in April. Or, worse yet, ride your motorcycle.
We’re here to help. Read on to learn about road closures in the Sierra Nevada.
Seasonal winter road closures
The Sierra Nevada range is high and rugged. Most of today’s mountain pass highways started out as primitive routes for wagon trains during the Gold Rush that started in 1849. Several have been improved and re-routed multiple times to accommodate modern vehicles and travel patterns. A few haven’t changed much, other than being paved, because the tough terrain didn’t allow it.
The standard for US Interstate Highways says that the maximum grade should not exceed six percent, or seven percent if the speed limit is less than 60 miles (97 kilometers) per hour. Ebbetts Pass and Sonora Pass both have grades that exceed 20 percent. On hairpin turns with steep drop offs. Even if you were able to drive these passes in the winter, you would probably not succeed. Imagine ice and snow, on a 20 percent downhill hairpin, with no guardrails, no cell service, and the nearest hospital is a couple of hours away. We’ll pass, unless there’s a snowmobile option.
Which passes are closed in winter
Seven of the 22 Sierra Nevada mountain pass roads close for the winter. They are:
- Donner Pass, Donner Pass Road
- Monitor Pass, CA 89
- Ebbetts Pass, CA 4
- Sonora Pass, CA 108
- Tioga Pass, CA 120
- Minaret Summit, CA 203
- Sherman Pass, Sherman Pass Road
Any of the other passes may be closed temporarily during and right after a winter storm. If there is snow on the road the highway might be open with chain controls.
When do the passes close for winter?
The passes close for the season when the first severe winter weather arrives in the Sierra. That usually happens sometime between mid-November and mid-December. It could be earlier. Occasionally, winter won’t arrive until early January, but that is quite unusual.
Monitor Pass, on Highway 89, is lower and a bit gentler than most of the other seasonal passes. If the winter weather is fairly mild, Monitor Pass may not close for the entire season. It might be closed for a few days or a few weeks at a time.
We publish and maintain a page that shows the seasonal winter closure and spring reopening dates for the major Sierra pass roads. This information was previously available on the Caltrans website. But it disappeared during a site overhaul in the summer of 2019. Our chart shows winter closures going back to November, 2010.
Donner Pass, on Donner Pass Road, is maintained by Nevada County, California. We have not been able to find an online source for seasonal closure dates on Donner Pass Road.
Sherman Pass, on Sherman Pass Road, is managed by Sequoia National Forest. We haven’t been able to find a good source of seasonal closure dates for Sherman Pass Road.
When do the passes open again?
The mountain pass highways open up again in the spring. Caltrans usually starts working to reopen the roads sometime in April. It takes several weeks to complete the job. Depending on how much snow has fallen over winter, and what the spring weather brings, the passes may open again anytime from late April to early June.
Getting the roads open again is more involved than just removing the snow. Severe winter weather can damage the roadways, guardrails, and other infrastructure. Sometimes huge boulders will have fallen and actually blocked the road. These need to be broken up with explosives and removed in pieces.
Late-winter weather in spring means that road crews have to move people and equipment off the seasonal mountain passes to keep other roads clear.
Temporary winter road closures
Just about any of the Sierra Nevada mountain pass roads can be closed because of winter weather. And depending on how severe that weather is the closure might last a few hours or a few days.
The highest passes are more likely to be closed than those at lower elevation. The year-round passes that are most likely to temporarily close for winter weather are:
- Mount Rose Summit, NV 431
- Carson Pass, CA 88
- Echo Summit, US 50
- Donner Summit, I-80
Carson Pass and Echo Summit both include sections where the road traverses a steep hillside that is prone to avalanches. Caltrans manages this by preemptively closing the road, intentionally causing avalanches, and then moving the snow off the road with heavy equipment.
Donner Summit on Interstate 80 is a major east-west transportation corridor. About 30,000 vehicles cross the summit per day. About 6,000 of those vehicles are semi-truck trailer rigs. Those trucks carry something between US$4 to $8 million in cargo over the Sierra each hour.
And the area gets an average of nearly 400 inches (10 meters) of snow per year.
If Donner Summit is closed, the best alternative route for trucks is 400 miles (about 650 kilometers) south at Tehachapi Pass.
Caltrans and the California Highway Patrol do everything they can to keep traffic moving over Donner Summit. When winter Sierra road conditions deteriorate, Interstate 80 will often be open when other mountain pass roads are closed. But still, it is closed several times each winter.
Check our Weather page to learn a lot more about the climate and seasons in the Sierra.
Current Sierra Nevada road conditions
The best source of current information on Sierra road conditions is the Caltrans QuickMap at quickmap.dot.ca.gov. It will even let you read highway message signs and watch live feeds from traffic cameras.
For roads in Nevada, see the Nevada Department of Transportation site at nvroads.com.
Road construction closures
Because winters in the Sierra are long, the road construction season is short. During summer and fall expect to encounter some road construction just about any time you cross the mountains.
Use the Caltrans QuickMap to check for construction zones on your route before you head out.
Wildfire closures
Wildfires in the Sierra can get so big that the authorities will close highways to keep the public safe and give firefighters space to do their jobs. Smoke can drift miles and reduce visibility to zero. Traveling through smoke will leave you with irritated eyes, nose, and throat.
Again, QuickMap is your friend. And you can get more information about individual wildfires from Cal Fire at http://www.fire.ca.gov/current_incidents.
Finally
So there you have it. The mountain pass roads you want to explore might be closed in winter. Or they might not. Or closed, partially, because of road construction. Or completely closed because of wildfires.
Traveling in the mountains requires you to be informed and have flexible travel plans. Good information about Sierra Nevada road conditions is readily available to help you plan and adapt as necessary.
Read our About the Passes page to learn much more about all the Sierra Nevada mountain pass roads.
