30 FORESTRY BULLETIN 



VARIABLE CLIMATE. 



The climate of Michigan is subject to wide variations, especially in the- 

 rainfall. The average rainfall, including snow, is 31.27 inches at the- 

 Agiicultural College, yet in 1894 the rainfall was only 19.3 inches, while- 

 in 1883 it was 48.36 inches. The fluctuations in temperature are less, the 

 mean temperature being 46.56, yet in 1871 it was 49.90, while in 1873 it 

 was 41.54 degrees, or more than eight degrees colder. 



To enable one to see at a glance the fluctuations in rainfall, and in tem- 

 perature above the frost point for the six growing months, from May to 

 October, the following plate is inserted: The heavy black horizontal line 

 denotes the relative amount of rainfall for the six months, while the verti- 

 cal heavy black line shows the normal rainfall for the period: The light 

 horizontal line shows the relative temperature above frost point for the six. 

 months of the year, and the light vertical line shows the normal tempera- 

 ture above frost point for the same period. 



The changes from year to year in the amount of rainfall are so great 

 as to be confusing in studying the weather. To equalize this in some de- 

 gree and see whether our climate is changing, the results are recast in 

 periods of five years, both in the annual rainfall and in that for six months 

 of the active growing season. 



Inches of mean rainfall by periods: Year. 6 months. 



1864 to 1868 31.70 17.67 



1869 to 1873 31.34 19.18 



1874 to 1878 31.88 17.23 



1879 to 1883 37.34 23.24 



1884 to 1888 ' 31.78 17.34 



1889 to 1893 28.34 18.22 



1894 to 1897 27.73 18.73. 



PROXIMITY TO THE GREAT LAKES. 



The influence of the great lakes on the climate of neighboring land,, 

 especially when the prevailing winds blow from the water over the land, 

 is recognized. To show the extent of this influence as far as possible, 

 observations were consulted in the office of the State Weather Bureau,, 

 and by the kindness of Director Schneider, are here presented. They cover 

 a period of ten years past, and embrace the mean temperature and rain- 

 fall for the six months — May to October: 



Temperature. Rainfall. 



Grand B[aven, Ottawa C< I. 60.60 18.38 



Hart, Oceana Go 60 . 71 17 . 06 



Ivan, Kalkaska Co 59.40 17.33 



Charlevoix, Charlevoix Co 59 . 39 16 . 83 



Cheboygan, Cheboygan Co 57.45 18.00 



Alpena, Alpena Co 56.63 19.89 



Harrisville, Alcona Co 59.48 18.15^ 



Jeddo, Sanilac Co .• 61.41 16.46 



Port Huron, St. Clair Co 60 . 53 16.91 



Grayling, Crawford Co 58 . 18 14 . 11 



Ovid, Clinton Co 61.60 15.70 



Alma, Gratiot Co 61.03 16.86 



Flint, Genesee Co 60.90 13.84 



Agricultural College, Ingham Co ... . -- - - 



