484 Eighth Annual Keport of the 



IV. PRECIPITATION. 



Annual Fluctuations of Rainfall. 



The fluctuations in the average or normal amount of rainfall 

 from month to month do not occur in a uniform manner over the 

 entire area of New York, but must rather be classed under sev- 

 eral quite distinct types depending ujjon atmospheric conditions 

 which have alreadv been summarilv described in section I. The 

 character of various types and their important modifications are 

 shown in oo'nsideraible detail by i)lates 2 and 3. It may be noted 

 that the irregular lines in the diagrams 'have no meaning other 

 than as coinneeting the points on the ordinates or verticals rep- 

 resenting the average monthly rainfall. 



A closie approtach to the continental type of rainfall, with its 

 early summer m-aximum, is found over the central plateau re- 

 gions (including the eastern and western plateaus fuwd the south- 

 ern Adirondack region) as represented by Cooperstown. Pro- 

 ceeding eastward to tiie central Hudson valley, a July maximum 

 is found which extends through the Cha.mi)laiin valley aud over 

 the Province of Quebec. In the southern Hudson valley the 

 maximum varies from July to August, while south of the High- 

 lands the August maximum obtains almost exclusively; also ex- 

 tending over Long Island to Setauket, but di-sappearing at East 

 Hampton and Block Island. The Great Lakes aiud St. Lawrence 

 valley show a June or July maximum, which, however, is sec- 

 ondarv to that of autumn. 



Autumn rains. — Over the State, generally, a large precipita- 

 tion obtains in October, as compared with the months immedi- 

 ately preceding and following. This constitutes the princijjal 

 maximum of the year at several stations of the St. Lawrence 

 valley, the central i>art of the Great Lake Region, central Long 

 Island and beyond the limits of New York, in New Brunswick, 

 •Nova Scotia and Ontario. Within this State and October mini- 

 mum is found only in the vicinity of New York city, but is a 

 feature common to the coast south of that point, and also ob- 

 tains at several places in the interioi* of New England. A rela- 



