Mean temper- ature, Fahr.: Yuma 54.1 58.8 64.5 69.8 77.2 84.9 91.5 90.7 84.4 73.0 61.9 56.0 72.2 Tucson 49.4 53.2 59.5 65.6 74.0 82.3 87.2 83.5 77.7 68.5 57.0 52.0 67.4 Mean precip- itation inches and hundredths): Yuma 0.42 0.51 0.26 0.07 0.04 T. 0.14 0.35 0.15 0.28 0.29 0.46 3.04 Tucson 0.75 0.98 0.90 0.17 0.16 0.19 2.86 3.08 1.16 0.33 0.37 0.95 12.26 Prevailing winds: Yuma N. N. W. W. W. SW. S. S. NE. NE. N. N. N. Tucson S. S. S. W. S. SW. SE. SE. S. S. S. SE. S. Average cloudiness (scale 0-10): Yuma 2.4 2.4 2.4 1.6 1.3 0.8 1.8 2.3 1.1 1.3 1.7 2.5 1.8 Tucson 3.0 3.2 3.2 1.8 1.6 1.5 4.5 4.4 1.9 1.6 1.6 2.9 2.6 The precipitation on the Sonoran province is chiefly in the form of rain; in the winter humid season snow falls frequently on the Sierra Madre and rarely on the outlying ranges; in both humid seasons (and in humid spots at all seasons) dew forms in greater or less abundance. Fog frequently gathers along the coast, especially during the winter and in the midsummer wet season, and sometimes drifts inland for miles. The mean annual precipitation may be estimated at 20 or 25 inches toward the crest and half as much toward the base of the high sierra; thence it diminishes coastward, probably to less than 2 inches; the mean for the extensive plains forming the greater part of the province may be estimated at 3 or 4 inches. The greater part of the precipitation is in local storms, frequently accompanied by thunder-gusts or sudden tempests, though cold drizzles sometimes occur, especially at the height of the winter humid season. Except where the local configuration is such as to affect the atmospheric movements, the distribution of precipitation is erratic, in both time and space; some spots may receive half a dozen rains within a year, while other spots may remain rainless for several years; and the wet spot of one series of years may be the dry spot of the next. The climatal features of Seriland are somewhat affected by the pronounced topographic features of the district. Snow sometimes falls on Sierra Seri, and probably on Sierra Kunkaak; gales gather about the rugged ranges at all seasons, and sometimes produce precipitation out of season; the extreme heat of midday and midsummer is tempered by the proximity of the tide-swept gulf; and since most of the local derangements tend to augment precipitation and reduce temperature, it would seem safe to estimate the mean annual rainfall of the tract at 4 or 5 inches, and the mean temperature at about 70°, with a mean annual range of some 30° and an extreme diurnal range of fully 80°.