The quality controlled Iowa COOP data for July 2015 has been uploaded to the IEM. These observations are kindly provided by Harry Hillaker, our state climatologist, who passes along these notes on the month:

General Summary. Temperatures averaged 72.2° or 1.4° below normal while precipitation totaled 5.78 inches or 1.28 inches above normal.   This ranks as the 27th coolest and 19th wettest July among 143 years of records.

Temperatures. Unseasonably cool weather prevailed early in the month with nine of the first ten days of July averaging cooler than usual.   Temperatures failed to exceed 90° anywhere in the state during those opening ten days of the month with afternoon highs reaching only 61° at Donnellson, Fort Madison, Keokuk and Burlington on the 8th.   The month’s lowest temperatures were recorded during this period with 44° readings at Cresco and Elkader on the 2nd and also at Spencer on the 3rd.   However, seven of the next eight days were warmer than normal.   Temperatures reached 97° at Des Moines on the 13th and at Bellevue, Lamoni and Osceola on the 17th.   Meanwhile the heat index (what the air ‘feels like’ when humidity is considered) reached 110° at Sioux City on the 12th, 111° at Burlington on the 13th and 110° at Burlington on the 17th.   The last one-third of the month was nearly evenly divided between above and below normal temperatures.   Hawarden recorded the highest temperature with 97° on the 24th while Burlington registered the highest heat index with 109° on the 28th.   Spencer Airport was the late-month cool spot with a low of 50° on the 21st.

Cooling Degree Days. Home air conditioning requirements, as estimated by cooling degree day totals, averaged 63% greater than last July (the fifth coolest July on record) but 12% less than normal.   Cooling degree day totals thus far in 2015 are running 9% greater than last year at this time, but 12% less than normal.

Precipitation. The first two weeks of July were relatively dry, bringing a statewide average of 1.61 inches of rain (normal = 2.28) while the remainder of the month brought an average of 4.17 inches of precipitation  (normal = 2.22).   The most noteworthy early month rain event brought 3 to 5 inches of rain to much of Muscatine and Scott counties on the night of the 6th.   Rains of 3 to 5 inches fell across much of Page and Taylor Counties on the night of the 15th.   However, the most concentrated period of rain came from the 24th to the 28th.   North central Iowa was the initial focus for heavy rains with Mason City Airport picking up 4.13 inches on the 24th.   The month’s heaviest rains fell across south central Iowa on the night of the 28th with Spring Hill (Warren County) picking up 6.32 inches.   Monthly rain totals were quite variable with much of northern Iowa recording below normal July rain totals while the southern one-third of the state (with the exception of Pottawattamie County) was very wet.   Rain totals varied from 1.20 inches at the Dubuque Airport to 13.33 inches at Knoxville.   Knoxville’s total was just shy of their July record of 13.58 inches set in 1958.

The following is the number of new daily records set at COOP sites based on data back to 1951.

                 __________2015__________________________2014____
                 JUL  JUN  MAY  APR  MAR  FEB  JAN  DEC  NOV  OCT
Maximum High:     22   69   28   34  182   13  113   84   24   97
Minimum High:    261   88  316   28  102  364   65   60  634   89
Maximum Low:      54   32   82   34   29   25  135  451    5   56
Minimum Low:     139   26   87   76   98  345  111   28  550   22
Maximum Precip:  214  151  155  122   17  113   67  121   67  149

The following is a table summarizing how well the IEM daily data estimator is working in comparison to the quality controlled data.

                 2015
                 JUL   JUN   MAY   APR   MAR   FEB   JAN
High Temp Bias   0.0   0.0  -0.1   0.0   0.3   0.3   0.2
High Temp STD    1.7   1.7   2.5   2.2   2.6   2.8   2.5
Low  Temp Bias   0.2   0.2   0.1   0.3   0.4   0.3   0.1
Low  Temp STD    2.0   2.0   2.0   2.7   2.9   2.9   2.6
Precip    Bias   0.00  0.00 -0.01  0.00  0.01 -0.16  0.01
Precip    STD    0.29  0.33  0.20  0.13  0.13  0.05  0.04