Corridors
Mammoth chain control: US-395 and SR-203 requirements today
Live chain control
Updated · Caltrans / NDOT data via Snowy Roads, refreshed every 3 minutes. Tap a chip for checkpoints, cameras and signs.
Chains are required for Mammoth whenever Caltrans posts R-1, R-2 or R-3 on US-395 or on SR-203 between the town of Mammoth Lakes and Main Lodge. Controls usually appear on the summits south and north of town and on the climb to the mountain. Today's status is shown above.
The roads to Mammoth
From Southern California. US-395 north through Bishop, then the Sherwin grade past Tom's Place and Crowley Lake to the SR-203 junction. SR-203 runs through the town of Mammoth Lakes and continues as Minaret Road up to Mammoth Mountain's Main Lodge. Canyon Lodge and Eagle Lodge are reached on town streets, which the town plows and Caltrans does not report on.
From the Bay Area and Sacramento. In winter the direct passes are closed, so the drive is US-50 through South Lake Tahoe and over Kingsbury Grade (NV-207) into the Carson Valley, then US-395 south through Gardnerville, Walker and Bridgeport, over Conway Summit and past Lee Vining and the June Lake junctions to Mammoth. This is the way Mammoth and June Mountain send winter drivers. Kingsbury is the steep part and the first to go under control: Nevada plows US-50 over Spooner Summit to Carson City ahead of it, so stay on US-50 when Kingsbury is bad, and I-80 to Reno and US-395 south is the long way round. Tioga Pass (SR-120), Sonora Pass (SR-108), Ebbetts Pass (SR-4) and Monitor Pass (SR-89) close for the winter, usually from the first big storm until late spring.
June Mountain is a few miles off US-395 on SR-158, the June Lake Loop, whose south junction sits just north of Deadman Summit.
Where the controls go up
Caltrans District 9 in Bishop posts the controls, and the US-395 page lists them by checkpoint. The usual places:
- SR-203 from Mammoth Lakes to Main Lodge. The steepest, highest and most frequently controlled stretch. Expect R-2 on the climb during and after any storm, and R-3 or a closure on the worst days. Mammoth Mountain's own shuttles and the parking at Main Lodge are the reason many locals leave the car in town.
- US-395 south of town. The Sherwin grade between Tom's Place or Crowley Lake and the SR-203 junction, where the road climbs from the Owens Valley.
- US-395 north of town. Deadman Summit between the Mammoth and June Lake junctions and Conway Summit north of Lee Vining, both above 8,000 feet and both exposed to wind.
- SR-158, the June Lake Loop, on the way to June Mountain.
Between storms the valley sections of US-395 dry quickly in the sun, and it is common to drive up from Bishop under R-0 and meet R-2 only on SR-203.
What a storm usually looks like
Eastern Sierra storms bring wind as well as snow, and ground blizzards on the open summits can close US-395 even when the total snowfall is modest. Caltrans holds traffic at Bishop, Lee Vining or Bridgeport when Conway or Deadman is blocked. SR-203 keeps its control longest because it climbs into the resort's snow. Requirements change without notice; the Mammoth page shows the SR-203 and US-395 checkpoints with cameras at Crestview, Conway Summit and Mammoth Mountain, refreshed every 3 minutes.
What the levels mean for your car
Under R-1 you need chains unless you have snow-tread tires; under R-2 unless you drive a 4WD or AWD vehicle with snow-tread tires on all four wheels; under R-3 everyone chains up. Exempt vehicles must still carry chains. See R-1 vs R-2 vs R-3 and chains for AWD, 4WD and snow tires.
Before you go
Always carry chains: on storm days the checkpoint at the bottom of Minaret Road turns around cars without them.
What history says
From the Snowy Roads chain-control archive for US-395 (US-395 S): what past winters looked like, not a forecast.
- Which level to expect. When chains were required here, it was R-1 67% of the time: cars with snow tires on the drive wheels could go without chains. Last 2 winters.
- How long it lasts. Half of the chain controls here ended within 18 hours; 33% lasted more than a day. Last 2 winters.
- Snow and chains. At Hartly Springs, chains went up a median 3 hours after snow began at Deadman Summit, and came off a median 13 hours after it stopped. Last 2 winters.
- Snowfall and chains. With 1 to 2 inches of snow in the previous 24 hours at Conway Summit, chains were up 70% of the time; with under 1 inch, 9%. Last 2 winters.
See every trend and chart on the US-395 page (Historical trends, under the chain-control card).
Chain-control history: Caltrans and NDOT postings archived by Snowy Roads. Weather by Open-Meteo.com (CC BY 4.0).
FAQ
Are chains required to get to Mammoth today?
Look at the US-395 and Mammoth chips in the live strip above, or open the Mammoth page for every checkpoint on US-395 and SR-203. R-0 means no control is posted.
Where is chain control usually posted for Mammoth?
On SR-203 between the town of Mammoth Lakes and Main Lodge first and most often, then on US-395 at the Sherwin grade south of town and at Deadman and Conway summits north of it.
Do I need chains on US-395 from Los Angeles?
Only when a control is posted, most often at the Sherwin grade climbing out of the Owens Valley. The valley floor from Lone Pine to Bishop is rarely under control.
How do I get to Mammoth from the Bay Area in winter?
Over US-50 through South Lake Tahoe and Kingsbury Grade (NV-207) into the Carson Valley, then US-395 south. That is the route both resorts give. When Kingsbury is under control or closed, stay on US-50 over Spooner Summit to Carson City; I-80 to Reno and US-395 south is the long way round. Tioga, Sonora, Ebbetts and Monitor passes are closed in winter.
Is June Mountain under the same controls?
The June Lake Loop, SR-158, has its own control, and the approach on US-395 crosses Deadman Summit from the south or Conway Summit from the north. The June Mountain page lists the checkpoints.