MARYLAND GEOLOGICAL SURVEY 181 



PRECIPITATION. 



Precipitation is an extremel}^ variable element of climate, and very 

 great differences may be found at stations not widely separated; no 

 corrections can be applied to short records of rainfall, and the averages 

 for the county have been obtained from the original uncorrected records 

 as given in Table IV. A critical examination of the records will lead to 

 the conclusion that probably the amounts at Cambridge and Jewell are 

 slightly above the true normals for the region, while at Charlotte Hall 

 they are below. 



Calvert County receives slightly over 42 inches of rain per annum. 

 While this amount is slightly less than that for most other counties 

 farther north-, it is not the lowest value in Maryland, which appears to 

 obtain in Allegany County, approximately 34 inches per annum." As in 

 all other counties of Maryland the precipitation is quite uniformly dis- 

 tributed throughout the year. The greatest average occurs in July, with 

 5.32 inches, which is 13 per cent of the annual total; and the least occurs 

 in November with 2.45 inches, which is 6 per cent of the annual amount. 

 Excessive precipitation is not frequent in Calvert County. A monthly 

 total of 10.00 inches may be considered excessive for the region under 

 discussion. No monthly total approaching this amount has been re- 

 corded at either Cambridge, Charlotte Tlall, or Solomons. At Jewell, 

 however, which is quite near the northern boundary of Calvert County, 

 an amount exceeding 10 inches has occurred three times during the past 

 15 years, namely in July, 1889 (10.25 inches), July, 1891 (12.15 inches), 

 and July, 1897 (19.90 inches). At all stations amounts less than 1.00 

 inch are not infrequent, and at Jewell only a "trace"' was received in 

 December, 1889. The absence of rainfall during an entire month is 

 certainly a condition usually associated only with the arid regions of the 

 West. The summer rainfall is heaviest in consequence of the greater 

 frequency of thunderstorms during that season; spring follows, while 

 autumn is the driest season of the year. 



Data are not available for finding the averages of other climatic ele- 



* The Climate of Allegany County, by O. L. Fassig, p. 225. 



