THE CLIMATE OF MICHIGAN. 



693 



TABLE VI.— ABSOLUTE MINIMUM TEMPERATURE (°F.) 



The tables above show the effect of Lake Michigan on the temperature of Grand Haven and Mil- 

 waukee. The average of five stations in South Dakota, Wisconsin and Iowa, having the same latitude 

 as Grand Haven and Milwaukee, were selected for comparison. The "difference" is the departure 

 between the reading at Grand Haven and the average of the five western stations, in each case. 



These tables show that the extremes of temperature experienced at 

 inland stations are not felt at Grand Haven, which is a typical lake 

 station. 



As already stated the frequent passage of cyclones and anti-cyclones 

 across the lake region causes fluctuating temperature to a greater extent 

 than is found in regions outside the storm path. In the winter season 

 the approach of a storm area from the west is preceded by southerly 

 wind and rising temperature in Michigan, and the high pressure area 

 which follows brings with it a shift of wind to the northwest, with 

 colder weather. In the summer season storm areas which move across 

 the northern portion of the Great Lakes, at a time when the pressure is 

 high over the southeastern states, cause hot waves in this state, but 

 these arie usually followed in a day or two by refreshing northerly breezes 

 attending approaching high pressure areas from western Canada. The 

 changeableness of the temperature is therefore one of the noticeable 

 features of the climate of Michigan. 



TRECIPITATION. 



Eaiii and snowfall should be next considered. The same four factors 

 which control the temperature of a place also influence, to a greater or 

 less extent, the amount of precipitation. The influence* of latitude is 

 not so pronounced on precipitation as on temperature. In fact within 

 the range of latitude found in Michigan no difference in rainfall due 

 to distance from the equator is noticeable. 



The effect of elevation is noticeable, however, perhaps to a greater 

 extent than on temperature. Chart VII, showing the normal precipita- 

 tion for the year over the state, if noted in connection with Chart 

 I, giving elevations, reveals the fact that rainfall usually increases with 

 altitude as a general rule. This is especially true on the western 

 slope of higher land. For example the heaviest rainfall in the state is 

 in the southern tier of counties, beginning about 25 miles from the lake, 

 where the elevation begins to increase toward the eastward. In the 

 upper peninsula the most rain falls in the interior counties, where the 

 elevation is greatest. In the elevated regions in the northern portion of 

 the lower peninsula, however, the rainfall is not greater than nearby 

 sections having less altitude. 



The Great Lakes undoubtedly increase the rainfall throughout this 

 whole region, but the annual amount of precipitation is not noticeably 



