New York Weather Bureau. 413 



the temperature in the northern and southern sections. A remark- 

 able case of this kind occurred on January 11, 1890, when the mean 

 daily temperature of stations in the St. Lawrence valley was fifty- 

 three degrees lower than that oibtainiing near the Pennsylvania 

 border. 



During the average winter month two or three storms pass north- 

 -eastward along the Atlantic coast. These are usually preceded by 

 an increase of temperature in the southeastern sections, and by a 

 decrease in the western and Great Lake regions. 



There exists an intimate relation between the character of the 

 air circulation and the precipitation of moisture over the State. 

 Our northwesterly winds are essentially dry, owing to the lack of 

 moisture in the continental interior, and also, in winter, to the cold- 

 ness of the air, which gives it a very small vapor carrying capacity. 

 Hence precipitation during the winter occurs almost entirely in 

 -connection with storm areas passing in the vicinity of the State, 

 and which mainly derive their supplj- of vapor from the inflow of 

 moist air induced by them from the Atlantic, or from the region of 

 the Gulf of Mexico. The heaviest precipitation accompanies the 

 Atlantic storms and those passing up the Mississippi and Ohio val- 

 leys to the Great Lakes; both of these classes of storms being 

 characteristic of the autumn and winter rather than of the summer 

 months. Hence, while the winter is the dryest season of the year 

 over the greater portion of New York, it brings a heavy precipita- 

 tion of rain and snow in the vicinity of the Atlantic coast, the 

 southwestern highlands of the State, and the region of the Great 

 Lakes. Over the Canadian provinces of Ontario and Quebec, the 

 winter precipitation is exceedingly small; and this characteristic 

 is shared by the St. Lawrence, Hudson and Champlain valleys and 

 the central plateau of New York. The supply of moisture from the 

 region of the Gulf of Mexico appears to be nearly exhausted before 

 reaching the Canadian provinces and the St. Lawrence valley, 

 4il though the southwestern Adirondack highlands receive a con- 

 ■siderable rain and snow fall from southwesterly winds; while the 

 moisture from the Atlantic is largely precipitated over the moun- 

 tains of New England and northern New York. 



