58S 



IOWA ACADEMY OF SCIENCE 



TEMPERATURE. 



Probably but few parasitic fungi are more sensitive to tem- 

 perature conditions than late blight. Its occurrence in Iowa 

 is dependent upon comparatively cool weather and in the cool 

 'climate of Maine upon comparatively warm weather. In both 

 instances the thermal mean for the years of its recurrence is 

 probably much the same. In one territory, its growth is limited 

 by too low a normal and in the other by one too high. 



The mean temperature in Iowa by months is given in the 

 table below: 



Mean Temperatures for Iowa. 



1885. The temperature was .l 3 below normal for June and 

 3.1" deficient for August. July averaged 1.8° above normal. 



1903. June — : 'The month just closed was the coldest June on 

 record for the period of 14 4 years." The daily mean was 5.6° 

 below normal. July — Daily mean 2° below normal. August — 

 3.1° below normal. 



1915. June — I 3 below normal. "The coldest June since 

 1903. At numerous stations the monthly mean and absolute 

 maximum temperature for the month was lower than ever *oe- 

 fore recorded in June." July — "With one exception the cold- 

 est July of record." ''August. 1915. was the coolest month of 

 that name in the climatological history of the state. The month- 

 ly mean temperature and the monthly extremes were all lower 

 than was ever before recorded and the daily means were below 

 the normal means on all but four or five days during the 

 month." Frost occurred in some part of Iowa in every month 

 of the year 1915. 



Taken as a whole, the years of outbreaks were distinctly cool 

 seasons. Subnormal temperatures were very pronounced for 



4 The climatological data of this bulletin are based upon the records of the 

 Iowa Weather Bureau. Thanks are due the director, G. M. Chappel. 



