have more than 200 perfectly clear days in a year; and many in
the mountains and in the south, even on the coast, have more than 250.
The extreme variability in the amount of rainfall is remarkable.[2] The
effects of a season of drought on the dry portions of the state need not
be adverted to; and as there is no rain or snow of any consequence on
the mountains during summer, a succession of dry seasons may almost bare
the ranges of the accumulated stock of previous winter snows, thus
making worse what is already bad.

The Colorado desert (together with the lower Gila Valley of Arizona) is
the hottest part of the United States. Along the line of the Southern
Pacific the yearly extreme is frequently from 124 deg. to 129 deg. 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 deg. to -36 deg. 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 37 deg. to 44 deg. F.; the
monthly means from 20 deg. to 65 deg. F. The normal annual means on
Indio, Mammoth Tanks, Salton and Volcano Springs are from 73.9 deg. to
78.4 F.; the monthly means from 52.8 deg. to 101.3 deg. (frequently 95
deg. to 98 deg.). The normal trend of the annual isotherms of the state
is very simple: a low line of about 40 deg. circles the angle in the
Nevada boundary line; 50 deg. normally follows the northern Sierra
across the Oregon border; lines of higher temperature enclose the Great
Valley; and lines of still higher temperature--usually 60 deg. to 70
deg., in hotter years 60 deg. to 75 deg.--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 examp