CLIMATIC INFLUENCES OF BODIES OF WATER 143 



Mississippi Valley were suffering from a hot wave and nine 

 stations reported temperatures of 100 F. or higher. There 

 were other days, however, on which the temperature of the 

 cities named was as high as that of the neighboring places. 

 Isolated instances such as those given do not prove any- 

 thing. In order to secure a clear idea of the conditions, it is 

 necessary to know the mean temperatures at the places 

 compared. 



The accompanying table gives the mean monthly tem- 

 peratures from many years' observations, as ascertained by 

 the United States Weather Bureau, for three cities located 

 on the shores of Lake Michigan and in the adjacent coun- 

 try. The mean monthly temperatures are definitely lower 

 during the summer months at the lake cities than at inland 

 points in approximately the same latitude. There is founda- 

 tion, therefore, for the belief that the shores of the lakes 

 offer more comfortable summer temperatures than may be 

 found at other places. The same conclusions would be 

 reached if other lake cities were compared with places 

 remote from the lakes. 



MEAN MONTHLY TEMPERATURES 



159. Lake and sea breezes. Those who live near the shores 

 of any large body of water are accustomed to attribute much 

 of their freedom from great heat to the breeze (fig. 73). This 

 breeze frequently blows on hot days and gives relief. Often 

 the morning is quite warm, with rapid increase of heat as 

 the sun gets higher in the heavens, until about ten o'clock, 

 when a cool breeze begins to blow from the lake and the 

 temperature becomes comfortable again. The breeze may 



