18 University of California Publications in Botany [Vol. 9 



paralleling the Pacific. The recorded temperatures of La Porte, in 

 Plumas County, near the northern limit of the region, and of Sum- 

 merdale, Mariposa County, in the southern half, are in close agree- 

 ment (table 1). These stations are both well up in the Transition 

 Zone. In the central Sierra, Cisco and Truckee are stations twenty 

 miles apart but on opposite sides of the divide (table 2). An inspec- 

 tion of these curves indicates that north and south distance has but 

 little influence on the local temperature; the northern station has a 

 slightly lower mean monthly temperature throughout the year and 

 monthly extremes a little below those of Summerdale. On the other 

 hand, location on opposite flanks of the range shows a marked differ- 

 ence in the monthly extremes and a significant difference in the yearly 

 means; Truckee is subject to winter minima far below the minima 

 at Cisco, and to summer maxima exceeding those at the western 

 station. The same relation is seen to exist between the temperatures 

 at Tamarack and Bodie (table 3). 



"Wliile very low minima or high maxima are not common in the 

 Sierra Nevada, they are by no means unknown. Above the transition 

 zone, minimum temperatures comparable to winter temperatures in 

 the eastern United States are recorded from some district of the Sierra 

 every season. The tables show the recorded extremes for a period 

 sufficiently long to give some conception of the probable range. Data 

 about winter minima from the very high mountain region are avail- 

 able from only three points. On Mt. Rose,^^ 10,800 feet, the highest 

 but one of the peaks in the Carson Range, during the years 1905-06, 

 1906-07, instruments recorded a minimum for the first year of 

 — 5° F. ; for the second, — 10° F. On Mt. Lyell, 13,090 feet, a 

 minimum thermometer was left for two years — July 1897 to July 

 1899.^* The lowest temperature for the first winter was — 13.6°, and 

 for the next, — 17.6° F. On the summit of Mt. Whitney,^^ maximum 

 and minimum thermometers left in September, 1909, showed a record 

 of 55° and — 23°, respectively, when read on May 24, 1910. Tlicy 

 were reset on September 26, 1912 and by the following spring, a 

 maximum of 65° and a minimum of — 35° had been recorded. The 

 data given in the temperature tables show that minima, comparable 

 to these from the highest peaks, are annual or nearly so, at Tamarack 

 and Bodie, some four to six thousand feet nearer sea level. 



The daily range of temperature in the High Sierra appears, from 

 the data at hand, to be considerably^ less than has been reported from 

 other similar regions in different parts of the world. A comparison 



