Arizona republican., 1908-04-01
THE CLIMATE OF THE
 SALT RIVER VALLEY.
By L. N. Jesunofsky, Section Director, U. S. Weather Bureau, Phoenix, Arizona.

ZS minutes, nortn, ana longitude IF degrees and co minutes, west. in a valley IS miles wide and some 70 miles in length. two miles distant from the Salt River. at an altitude of HOS feet above sea level, Phoenix possesses fully as many distinctive climatic features relating to dry atmosphere, bright sunShiny days, marked absence of windstorms and freedom from ice and snow as other localities more favor ably situated.
 In the matter of temperature, the seasonal averages presented herewith show a modification of climatic condi- tions essentially healthful and salubri- ous. Thesaverage of spring is 61.l de- grees; summer, SIS degrees; autumn. 7l.3 degrees: winter. 53.2; annual aver age, 699 degrees. The period of ex- treme heat usually begins about the 10th of June and continues until the 10th of September. There are a few days during the last decade in May and the first decade in June on which the maximum temperature readings exceed 100 degrees.
 The period of extreme cold includes ihe dates from the 18th of December to the 18th of February. During the fore part of December and the latter part of February, the temperature occa- SiOnally reaches the freezing point.
 The highest temperature recorded at Phoenix during the past F years was IT. degrees on July 3, 1907; the lowesi was % degrees, on December q, 1900. The average number of days on which the temperature reaches the freezing point is as follows; In January. six days; February. three: December, four The average number of days on which the temperature reaches 100 degrees and above is as follows: In May, two days; June. seventeen; July. twenty five; August. twenty; September. seven.
 Frequently those tremendous banks of cold air. designated as cold waves, deviate from their normal paths and sweep far southward over the Rocky Mountains causing minimum tempera- ture readings of 10 degrees to 2a de- grees below zero over northern Ari- zona. Utah. Colorado. Nevada and Northern New Mexico. In such cases their force becomes expended and they are much less intense after reaching the central plateau of Arizona. within the region of the Salt River valley. In these extreme cases, it is seldom that the temperature remains below the freezing point for more than one to four hours at time.
 The occurrence of the first and last frost has. also. great bearing on the climate and productions of this locali- ,,, hot sr fs. 1f tl,a t.a-t sV,- terest to the florist. farmer and grow CT of fruits and vegetables. The earli- est date on which the first killing frost occurred in autumn. during the past l2 years, was November s, 1S91. The average date on which the first killing frost occurs in autumn. is December .. The average date on which the last killing frost occurs in spring. is February g. The latest date on which the last killing" frost occurred in spring. was March q. lS97. Roses bloom and garden vege- tables grow all the year around in Phoenix. Oranges, of four different varieties. lemons. of three varieties. and grapefruit. of three varieties. un- eXcelled in quality, are grown in large quantities from October 5th to March lst The crops of l9O7-190S were the largest in the history of the valley. Other fruits. of fine quality, such as the almond, apple, apricot, peach. date. pear. plum. cherry, strawberry, pome- granite, olive, grape. fig and mulberry, are grown in abundance Five to sev- en cuttings of alfalfa are made from March 18th to December 18th. Barley. oats and wheat. planted from october 15 to February 18th, natures by May 18th.
 With reference to the meteorological conditions in the Salt River valley, there are certain characteristics that distinguish it from many other sec tions of the country. Chief among these being the constant or regular conditions. having no reference to an eouable climate Not being within the path of storm frequency, the se- quence of weather is more uniform than in more northern attitudes. The rainfall is small; there is an absence of clouds; insulation by day and radi- ation by night are both strong and rapid; the range of temperature from day to night is large. from 9 degrees to 8 degrees; the winds are light and the evaporation is usually high" The large daily amplitudes in temperature are accounted for by the fact that there is much dryness of the air and the skies are almost cloudless.
 The general opinion as to the preva- lence of excessive heat in the Salt River valley is, 10 marked degree. somewhat misleading. Even the com parisons of temperature of its warm est days, with readings made in the middle west, are most favorable. High day temperatures are invariably ac- companied by low humidity. which are scarcely comparable with high tenn peratures and excessive humidity as are experienced in other sections.
 The appended tabular statement was compiled to show the comparisons of temperature between the middle western states and the Salt River val ley.
 Table of maximum and minimum temperature readings made at selected stations in the middle west and the including the Salt River