698 



STATE BOARD OF AGRICULTURE. 



east instead of west then it would be the Lake Huron shore that would 

 have the more equable clinuite. 



Michigan is, of course, in the region of the prevailing westerly winds. 

 Chart X shows the prevailing direction at each observing station in the 

 state. Local inlluences such as the contour of the land and the proximity 

 of the Lakes cause a deviation from the true west, at some stations. 

 The ''land and sea breeze" is pronounced along the lake shores. This 

 is a local wind, blowing on shore in the lieat of the day and toward the 

 water at night, due to convection. The air becomes hot and ligiiter over 

 the land than over the water on a hot summer day, and the cooler and 

 heavier air over the cool water moves in, forcing it upward. Just the 



TABLE VII. — This table shows the number of rainy, clear, partly ckudy and clcudy days in each 

 month and for the year in each of four sections of the state. A "Rainy" day is one with 0.01 inches 

 or more of rain or melted snowfall, a clear day is one with zero to thrre-tenths clouds, a partly cloudy 

 day, four to seven-tenths of clouds, and a cloudy day ejght to ten-tenths overcast. 



opposite action takes place at night, when the laud becomes cooler than 

 the lake. These cool, refreshing lake breezes are very welcome on a 

 hot summer afternoon, but in the early spring they are often too cool 

 to be pleasant. The temperature often falls thirty degrees or more within 

 a few minutes when the wdnd shifts, on a warm spring afternoon. 



As has already been stated the passage of areas of low and high pres- 

 sure across the Great Lakes region is attended by shifting wdnds. The 

 currents of air flow spirally inward toward the centers of low barometer, 

 counter-clockwise, while in the high pressure areas the wdnds blow 

 spirally outward from the center, in a clockwise direction. When a 

 cyclone approaches from the west, therefore, the winds are first south- 

 easterly, shifting around either through east and north, or through 

 south and southwest, depending, of course, on the path the storm takes, 

 changing in the former direction if tlie storm passes south of the ob- 

 server, and in the latter direction if the center is to the northward. 



