FIFTEENTH ANNUAL YEAR BOOK— PART XI 763 



Pressure. — The mean sea level pressure for the State was 29.93 inches. 

 The highest recorded was 30.34 inches, at Dubuque, on the 16th; tlie 

 lowest, 29.49 inches at Sioux City, on the 4th. 



Temperature. — The monthly mean temperature for the State, as shown 

 by the records of 108 stations, was 72.2°, or 3.1° higher than the normal. 

 The highest monthly mean was 77.6° at Leon; the lowest was 67.2° at 

 Elma and Estherville. The highest temperature reported in the State, 

 was 101° at Burlington on the 9th and 26th and at Centerville on the 9th, 

 and the lowest was 40° at Alton on the 2d and at Monroe on the 17th. 

 The temperature was quite uniform throughout the month, which will 

 account for the unusually rapid growth of vegetation. 



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

 76 per cent, and at 7 p. m., 59 per cent. The mean for the month was 

 68 per cent, or about 2 per cent less than the normal. The highest 

 monthly mean was 70 per cent, at Dubuque, and the lowest, 65 per cent, 

 at Des Moines. 



Precipitation. — The average for the State, 116 stations reporting, was 

 5.57 inches, or 1.19 inches more than the normal. By sections the aver- 

 ages were as follows: Northern, 6.94 inches, or 2.51 inches more than 

 the normal; Central, 6.08 inches, or 1.76 inches more than the normal; 

 Southern, 3.68 inches, or 0.71 inch less than the normal. The greatest 

 amount reported from any station was 13.24 inches at Osage, and the 

 least 1.17 inches at Bonaparte. The greatest amount in any 24 consecu- 

 tive hours, 6.31 inches, occurred at Osage. During 12 hours and 13 

 minutes, 4.33 inches fell at Davenport on the 4th-5th. 



The rainfall was well distributed throughout the month, except in 

 many localities over the southern counties, where but little rain fell 

 during the latter half of the month. Measurable precipitation occurred 

 on an average of 13 days. 



Wind. — The prevailing direction of the wind was from the south. 

 The highest velocity recorded was 67 miles an hour, from the south, 

 at Sioux City, on the 23d. As in May, wind squalls were frequent, and 

 damaging in many localities. 



Sunshine and Cloudiness. — The average duration of sunshine was 

 about 70 per cent, or about 5 per cent more than the normal. The 

 average number of clear days was 12; partly cloudy 14; cloudy 4. 



Miscellaneous Phenomena. — Thunderstorms occurred at some place 

 in the state on every day of the month, except the 2d, 16th, and 29th, 

 and hail fell on the 4th, 5th, 6th, 10th, 12th, 14th, 21st, 22d, 24th, 25th 

 and 26th. 



RrvEES. — Owing to heavy rains in northern Iowa, Minnesota, Wiscon- 

 sin, and the Dakotas, there was a moderately high stage of water in 

 all rivers, but no damaging floods occurred except in some of the smaller 

 streams in the northern part of the State, where bottom lands were 

 flooded and crops were more or less damaged. 



