It snows alot at Mammoth, and much of the winter snow lingers into summer. Many roads in the area are plowed and open year round (including the road to Mammoth Mountain Ski Area), but some are not, and don't open until sometime in summer. On a typical year, the road to Devils Postpile (which we had planned to visit) opens in late May/early June. Although we arrived on June 24, the road had not yet opened because of particularly heavy snowfall. Before you go on a trip to someplace like Mammoth, always check first to see when roads and facilities will open.
R-1 Chains are required on all vehivles under 6,000 pounds except those equipped with snow tires on the drive wheels. vehicles over 6,000 pounds are required to place chains on the drive wheels.
R-2 Chains are required on all vehicles except four-wheel drives equipped with snow tires on all four wheels.
R-3 Chains are required on all vehicles without exception.
The penalty for failure to observe the posted chain controls may include a citation and a severe fine. So remember to always carry chains and use them when required to do so.
Just because its winter and theres snow dont think you cant get a sun burn. Sunblock is very important because befor you know it you can get burned pretty bad. Also, you can end up looking like a raccoon.
If you are hiking and skiing, learn about avalanche safety. When I was here in the 80s we were young and stupid too, and amazingly lived to tell about it. However, we cut off some huge avalanches that would have killed everyone if we had just been a few feet to the right or left. This is a hard lesson for people to learn since everyone thinks that snow is 'light and fluffy.' It isn't...it can be like cement.
The only thing to worry about are blizzards in the winters. If it is bad enough, the roads will be closed and you will be stuck up there a little longer than expected. But hey, Mammoth is a great place to be stranded at! :)