140 DAVENPORT ACADEMY OF SCIENCEvS. 



"Too far inland to receive the equalizing effects of winds blow- 

 ing directl}' from the ocean, the climate of Iowa is strictly conti- 

 nental in type. This implies a very wide range of temperature, 

 winters of considerable severity, summers of almost tropical heat, 

 and a large percentage of sunshine as compared with insular 

 regions. As there are no mountain ranges nor considerable dif- 

 ferences in the altitude of the several sections, the climate of the 

 state is quite homogeneous." 



The records of the Iowa Weather and Crop Service for the past 

 thirteen years show the average amount of rainfall precipitated 

 to have been 31.07 inches. The southeast district has a 5^earl5' 

 average of 5.49 inches more than the northwest district and 1.05 

 inches more than the southwest district. The average annual 

 rainfall of the three Mi.ssissippi River districts is 30.04 inches. 

 These figures show a quite regular gradient of decrease in yearly 

 amount of rainfall from south to north as well as from east to 

 west . 



"The mean temperature of the state is 47.5°. Bj^ sections the 

 mean temperatures are as follows: Northern .section, 45.7°; cen- 

 tral section, 47.3°; southern section, 50°. 



"In this part of the Mississippi Valley the summers are warmer 

 and the winters colder than on the same parallels near the Atlantic 

 coast. In July the 75° isotherm passes through the southern 

 half of Iowa, dips southeastward below Cincinnati, passing 

 between Baltimore and Philadelphia. The mean maximum of the 

 state for July is 85°, and the midsunnner temperature is about as 

 high as that of Virginia and North Carolina. In January the 

 larger part of Iowa is within the i.sothermal belt 15'^ to 20°. These 

 lines run northeastward through northern Michigan, Ontario, 

 northern New York, Vermont, New Hampshire, and Maine. 

 The midwinter temperature corresponds to that of the vicinity of 

 Montreal, while the summers are as warm as at Washington, D. 

 C., and Richmond, Va. The winters, however, are shorter than 

 in the same latitude in the Atlantic states. The transition from 

 winter to summer is usually quite rapid, the average increase in 

 temperature in April being more than half a degree daily. The 

 daily mean of April is 17° higher than that of March, and May 

 averages ii'^ per day higher than April. . . . The records of the 

 United States Weather Bureau, covering a period of about thirty 

 years, show that the average date of the latest killing frost in the 

 spring has been April 20th, and the earliest in autumn October 

 9th. In every season there have been light frosts at later and 

 ealier dates, causing no appreciable damage to vegetation. 



"A distinctive feature of the climate as compared with the 



