FOURTH ANNUAL YEAR BOOK — PART II, 



139 



MONTHLY AND ANNUAL MEAN TEMPERATURES FOR THE ST ATE -1890-1902. 



(DEGREES. ) 



LATE AND EARLY KILLING FROSTS. 



In common with other portions of this country, this state is subject in the 

 crop growing season to occasional depression of temperature down to the 

 frost line. On the average, however, there is immunity from killing frosts 

 for a period of about 170 days. The records of the United States Weather 

 Bureau stations, 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 earlier dates, causing no appreciable damage to vegeta- 

 tion, but extensive injury to staple crops by heavy frost has occurred at very 

 infrequent intervals within the past thirty years. In 1870 Prof. T. S. Parvin 

 wrote as follows: ' "It has happened but once or twice in the last thirty 

 years that the frost has, over a great extent, seriously injured the corn crop. 

 When the spring is late, the fall is either quite hot or lengthened so as to 

 afford time for the crop to mature." The records covering the period since 

 1870 confirm this statement. The following tables show the dates on which 

 the latest and earliest frosts have occurred at the United States Weather 

 Bureau stations since their establishment: 



