18 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[18 



Table 1 



DATA ON THE LAKES OF THE OCONOMOWOC-WAUKESHA GROUP 



(Compiled from Birsre & Judav) 



CLIMATOLOGY 



Waukesha county lies within the zone of influence of Lake Michigan, 

 which tends to temper the summer heat. Winds off the lake lower the 

 temperature and tend to increase the relative humidity. Winters are 

 ordinarily severe, with the temperature dropping as low as —28 (Jan. 17, 

 1924). Precipitation (Fig. 10) is abundant and affords an enormous supply 

 of water directly to the streams and indirectly to the lakes. This causes a 

 seasonal fluctuation in the water level of the lakes, which has a certain 

 influence upon some species of fish. It is of particular importance to the 

 pickerel (Esox lucius) as the excessive amount of water inundates the 

 swamps bordering the lakes, affording excellent weedy breeding grounds 



