California (source: Encyclopedia Britannica 1911 Edition)
Along the line of the Southern Pacific the yearly extreme is frequently from 124° to 129° F. (i.e. in the shade, which is almost if not quite the greatest heat ever actually recorded in any part of the world). At the other extreme, temperatures of -20° to -36° are recorded yearly on the Central (Southern) Pacific line near Lake Tahoe. The normal annual means of the coldest localities of the state are from 370 to 44 F.; the monthly means from 20° to 65° F. The normal annual means on Indio, Mammoth Tanks, Salton and Volcano Springs are from 73.9 to 78.4 F.; the monthly means from 52.8° to 101.3° (frequently 95° to 98°). The normal trend of the annual isotherms of the state is very simple: a low line of about 40° circles the angle in the Nevada boundary line; 50° normally follows the northern Sierra across the Oregon border; lines of higher temperature enclose the Great Valley; and lines of still higher temperature—usually 6o° to 7o°, in hotter years 6o° to 75°—run transversely across the southern quarter of the state. Another weather factor is the winds, which are extremely regular in their movements.. There are brisk diurnal sea-breezes, and seasonal trades and counter-trades. Along the coast an on-shore breeze blows every summer day; in the evening it is replaced by a night-fog, and the cooler air draws down the mountain sides in opposition to its movement during the day. In the upper air a dry off-shore wind from the Rocky Mountain plateau prevails throughout the summer; and in winter an on-shore rain wind. The last is the counter-trade, the all-year wind of Alaska and Oregon; it prevails in . winter even off Southern California. There is the widest and most startling variety of local climates. At Truckee, for example, lying about 5800 ft. above the sea near Lake Tahoe, the lowest temperature of the year may be-2.5° F. or colder, when 70 M. westward at Rocklin, which lies in the foothills about 2 50 ft. above the sea, the mercury does not fall below, 28°. Snow never falls at Rocklin, but falls in large quantity at Truckee; ice is the crop of the one, oranges of the other, at the same time. There are points in Southern California where one may actually look from sea to desert and from snow to orange groves. Distance from the ocean, situation with reference to the mountain ranges, and altitude are all important determinants of these climatic differences; but of these the last seems to be most important. At any rate it may be said that generally speaking the maximum, minimum and mean temperatures of points of approximately equal altitude are respectively but slightly different in northern or southern California? Death Valley surpasses for combined heat and aridity any meteorological stations on earth where regular observations are taken, although for extremes of heat it is exceeded by places in the Colorado desert. The minimum daily temperature in summer is rarely below 70° F. and often above 90° F. (in the shade), while the maximum may for days in succession be as high as Iso° F. A record of 6 months (1891) showed an average daily relative humidity of 3o•6 in the morning and 15.6 in the evening, and the humidity sometimes falls to 5. Yet the surrounding country is not devoid of vegetation. The hills are very fertile when irrigated, and the wet season develops a variety of perennial herbs, shrubs and annuals. Fauna.—California embraces areas of every life-zone of North America: of the boreal, the Hudsonian and Canadian subzones; of the transition, the humid Pacific subzone; of the upper austral, the arid or upper Sonoran subzone; of the lower austral, the arid or lower Sonoran; of the tropical, the " dilute arid " subzone. As will be inferred from the above 2 The means for Los Angeles and Red Bluff, of Redding and Fresno, of San Diego and Sacramento, of San Francisco or Monterey and Independence, are respectively about the-same; and all of them lie between 56° and 63° F. The places mentioned are scattered over 31° of longitude and 6i° of latitude. account of temperature, summer is longer in the north, and localities in the Valley have more hours of heat than do those of south California. Hence that climatic characteristic of the entire Pacific Coast—already referred to and which is of extreme importance in determining the life-zones of California—the great amount of total annual heat supply at comparatively high latitudes.