534 IOWA DEPARTMENT OF AGRICULTURE 



Humidity. The average relative humidity for the State at 7 a. m. was 

 75 per cent, and at 7 p. m. it was 57 per cent. The mean for the month, 

 66 per cent, is about 1 per cent above the normal. The highest monthly 

 mean was 69 per cent, at Davenport, and the lowest was 62 per cent, at 

 Des Moines. 



Precipitation. The average precipitation for the State, as shown by the 

 records of 113 stations, was 6.87 inches, or 2.30 inches more than the 

 normal. By divisions the averages were as follows: Northern, 7.24 inches, 

 or 2.76 inches more than the normal; Central, 7.26 inches, or 2.67 inches 

 more than the normal; Southern, 6.11 inches, or 1.47 inches more than the 

 normal. The greatest amount, 11.98 inches, occurred at Gilman, and the 

 least, 2.72 inches, at Glenwood. The greatest amount in 24 consecutive 

 hours, 4.81 inches, occurred at Gilman, on the 24th. 



Snowfall. The average snowfall for the State was a trace, or 0.1 inch 

 less than the normal. 



Wind. The prevailing direction of the wind was from the southwest. 

 The highest velocity reported from a regular Weather Bureau station was 

 at the rate of 60 miles an hour from the west, at Sioux City, on the 9th. 



Sunshine and Cloudijiess. The average per cent of the possible amount 

 of sunshine was 66 or about 4 per cent more than the normal. The per 

 cent of the possible amount at the regular Weather Bureau stations was 

 as follows: Charles City, 51; Davenport, 72; Des Moines, 76: Dubuque, 

 67; Keokuk, 70; Sioux City, 62; Omaha, Nebr., 67. 



Miscellaneous Phenomena. Aurora, 16th. Fog, 13th, 14th, 18th, 29th, 

 30th. Frost, 1st. 11th, 13th, 14th, 20th, 23d. Hail, Northern Division, 6th, 

 8th, 9th, 17th, 19th, 21st; Central Division, 8th, 9th. 17th, 18th. 19th, 20th, 

 21st, 22d, 25th, 26th; Southern Division. 8th, 9th, 19th. 21st. 22d, 23d, 24th, 

 26th, 27th, 28th. See note below. Halo (lunar or solar) 7th. 10th, 

 11th, 20th, 25th. Sleet, 13th. Thunderstorm, 6th, 7th, 8th, 9th, 10th, 13th. 

 14th, 15th, 17th, 18th, 19th, 20th, 21st, 22d, 23d. 24th, 25th, 26th, 27th, 28th. 

 29th, 30th, 31st. Tornadoes. 8th, 9th, 19th, 21st, 31st. 



Rivers. The rivers were below normal stages till about the middle of 

 the month when the increased rainfall caused about the normal rise 

 approaching the usual early summer maximum." Excepting slight over- 

 flows in some of the interior rivers of the eastern part of the State 

 near the close of the month, the stages were generally moderate. 



HAILSTORMS OF MAY, 1918. 



M. V. Robins. 



On the 6th light hail fell in Franklin County, and on the 8th and 9th a 

 number of storms occurred, but on neither date was any serious damage 

 reported, although in Jefferson County and southeast of Sanborn, O'Brien 

 County, large hail fell. Hampton reported hail varying in size from one- 

 fourth inch to one and one-fourth inches in diameter, but little harm 

 resulted except that windows were broken and the soil packed by the 

 stones. Grinnell reported a fall of moderate sized stones that injured 

 tender plants and did considerable damage to greenhouses, and Mt. 

 Pleasant a storm with but little damage. On the 9th hail fell in scattered 



