WEATHER CONDITIONS ON THE PACIFIC COAST 

 The reader can obtain detailed information re- 

 garding the weather in various parts of the State 

 by referring to the bibliography at the end of this 



?aper: For San Francisco (McAdie, 1912), (McAdie, 

 913); for Berkeley (Reed, 1913); for Lick Ob- 

 servatory (Reed, 1914); for San Diego (Carpenter, 

 1913). The following condensed data for San 

 Francisco may prove of interest: 



Pressure. Mean annual pressure 1017 kilobars 

 (763 mm. or 30.03 in.); highest pressure 1036 kb. 

 (777 mm. or 30.60 in.) ; lowest pressure 985 kb. 

 (739 mm. or 29.10 in.). The absolute range of 

 pressure 51 kilobars, i. e., in equivalent force units, 

 51,000 dynes or 5 per cent of an atmosphere. 



Temperature. San Francisco has a compara- 

 tively small range of temperature. The annual 

 mean, based upon records covering a period of 

 forty years, 1871 to 1911, and obtained from the 

 mean of the daily maximum and minimum read- 

 ings, is 286 A. (56 F.). A truer value determined 

 from the 24-hourly readings for a period of twenty 

 years, 1891 to 1910, is 285.6 A. (54.6 F.). 



The departures from the mean are comparatively 

 small in all months. The warmest month is Sep- 

 tember, with a mean of 288 A. (59.1 F.), and the 

 coldest month, January, 282.6 A. (49.2 F.). The 

 warmest month has practically the same departure 

 above the mean as the coldest month has below. 

 The annual amplitude is 5.5 A. (9.9 F.). 



The monthly mean temperatures determined 

 from hourly readings are: 



January _ 283 49 July 289 56 



February 284 51 August 287 67 



March .. 285 52 September 288 59 



April 285 54 October 288 58 



May 286 '56 November 286 55 



June _ 287 56 December 283 50 



The coldest month was January, 1890, when 

 the mean temperature was 281 A. (46 F.), and the 

 warmest month, September, 1889, when the mean 

 was 291 A. (65 F.). 



In an average year there are approximately 

 1311 hours when the temperature is above 289 A. 

 (60 F.) ; 4111 hours when the temperature is above 

 286 A. (55 F.); and 7625 hours, or about 87 per 

 cent of the entire year, when the temperature ex- 

 ceeds 283 A. (50 F.). 



Differences between day and night tempera- 

 tures are small. The warmest hour, 2 P.M., has a 



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