The Sierra Crest is noted for having the capacity to produce four seasons of weather during a single Summer Day. Rain, snow, hail, fog, lightening, and a bit of sunshine can all happen in quick sequence.
This is especially true in the Central Sierra, where the elevations increase from those of the Northern Sierra Nevada.
The High Sierra is noted for rapid changes in weather and temperature, and the sudden appearance of harsh weather trends. You may experience anything from intense heat to bitterly cold Summer snow storms. Or you may not. In any case, weather must be considered and preparations made to deal with these weather facts BEFORE entering the High Sierras.
Long Distance Backpackers who were on the High Sierra Crest in early August of 2009 experienced just such a series of Summer Snow Storms.
Temperatures dropped to the high teens and low twenties, snow and hail fell which partially obscured the trails, and all of those who entertained the misconception that the Sierras only have fine weather during the Summertime were bitterly disappointed. Luckily for the many backcountry travelers who were not properly prepared, those storms blew apart, rather than consolidated and deepened.
Weather considerations should guide your gear selection.
Weather Preparations for Backcountry Travel
The Northern Sierra General Information
NWS Western US
NWS Water Vapor Western US 28 KM
GOES NE Pacific Watar Vapor
The NWS Radar out of the San Joaquin Valley covers the Souther half of the Sierra.
The NWS Radar out of Reno covers the Northern Sierra from Lake Tahoe down to Mammoth Lakes.
The NWS Pacific Southwest Radar covers all California, and can be clicked for local detail.
NWS Western Slope N Sierra to Yosemite
NWS Yosemite to Kings Canyon
Real-Time Ground Reporting Stations
Meso-West North California Map
Meso-West South California Map
For more detailed information see the area links above.