Adapted from Yosemite National Park by Jeffrey P. Schaffer

Of all influences, temperature and precipitation are probably the most important. The pertinent climatic data for Yosemite National Park and the lands to the west and east of it are summed up in the following table. The climatic sites are arranged from west to east in ascending order to Mt. Dana, then in descending order on the Sierra's steep east slopes down to Mono Lake. Note in this table that temperature decreases with increasing elevation, and that precipitation increases only up to mid-elevations, beyond which it decreases slowly to the crest, then rapidly beyond it.

Ellery Lake seems to be an exception. Its high precipitation figure is due to storm winds whipping through Tioga Pass, spreading out, and depositing their snow down-canyon around this lake. In like manner, stormy winds whip up the deep Middle Fork San Joaquin river canyon, cross the low Sierra crest, and deposit a thick mantle of snow in the Mammoth Mountain ski area, giving it one of the longest lasting ski seasons in the state.

Because much of a winter's snow remains through late spring-and some remains throughout summer-most of Yosemite's vegetation has an adequate water supply. In fact, the presence of the subalpine meadows is due to too much water, for conifers aren't able to survive in these seasonally water-saturated soils. However, on the rocky slopes of Mt. Dana, the Dana Plateau, and other alpine slopes, the snow often melts before the start of the growing season. On these dry slopes, then, the wildflowers are often dependent on summer thunderstorms for moisture. The winter snow on these slopes serves a different purpose for their perennial wildflowers: it buries and protects them. In extremely cold winter winds the equivalent wind-chill temperature can easily drop below -40:F (-40:C).