THE CLIMATE OF MICHIGAN. 685 



goes the more pronounced is the turn to the northward in the middle- 

 western states. As a result the majority of storms pass the region of 

 the Great Lakes and drift eastward out the St. Lawrence valley. These 

 storm areas bring with them the typical change to warmer and un- 

 settled weather, with rain or snow, according to the season. 



Following these disturbances areas of high pressure or anti-cyclones 

 usually arrive, bringing with them just the opposite sort of weather. 

 Most of these formations first appear on the weather map in the far 

 Northwest whence they move southeastward, many of them toward 

 the Great Lakes. As the air flows out away from these areas, as cold, 

 icy blasts in winter, the wind is northwest in advance of one of these 

 anticyclones, sometimes reaching the required severity to be termed 

 a "Cold wave." Now Michigan is in the direct path of the majority 

 of both the cj'clones and anti-cyclones, and the weather therefore swings 

 back and forth from one type to the other in irregular intervals of three 

 to five days. Rainfall is more or less evenly distributed throughout 

 the year and monotonous periods of extreme conditions of any kind 

 are infrequent and shore in duration. On the other hand regions remote 

 from these storm paths are not so evenly watered and do not experience 

 the fluctuating conditions of this section. 



^& 



PART II. 



THE CLIMATE OP MICHIGAN. 



Having outlined the factors which control climate in general the 

 peculiarities of the climate of Michigan will be more easily accounted 

 for. The various elements which make up climate, i. e., temperature, 

 precipitation, cloudiness, wind and humidity, will be taken up separate- 

 ly as they are found in this state and described in order. 



Michigan lies almost entirely between 42° and 47° N. latitude, and is 

 therefore about the same distance north of the equator as France, 

 Switzerland, northern Italy, Austria and the Balkan States. Its climate 

 is somewhat colder than the first three countries named but about the 

 same in temperature as Austria and the northern portion of the Balkans. 

 The ocean currents tend to cause milder weather in the three former. 

 The average annual temperature ranges from about 39° F. in the coldest 

 portions of the upper peninsula to 49° F. in the southern tier of counties. 

 Chart II shows the isothermal lines for the year, and they indicate 

 clearly the decrease in temperature with increase in latitude. The effect 

 of altitude can be noticed by studying the elevations shown in Chart 

 I in connection with the annual temperatures. The following will serve 

 to illustrate this effect: 



