The quality controlled Iowa COOP data for August 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. August temperatures averaged 69.2° or 2.3° below normal while precipitation totaled 5.41 inches or 1.21 inches above normal. This ranks as the 27th coolest and 21st wettest August among 143 years of records.

Temperatures. Summer heat was infrequent during August with daily low temperatures in the forties occurring on more days during the month (nine) than daytime highs in the nineties (seven days). Donnellson reported the month's highest temperature with a 94° reading on the 2nd while Sheldon and Spencer recorded the lowest temperatures with 40° readings on the morning of the 25th. Below normal temperatures prevailed for 13 consecutive days from the 18th through the 30th with five days during this period bringing daytime highs that were only in the sixties. "Highs" of only 61° occurred at Anamosa and Northwood on the 19th and also at New Hampton and Osage on the 28th.

Cooling Degree Days. Home air conditioning requirements, as estimated by cooling degree day totals, averaged 21% less than last August and 24% less than normal. Cooling degree day totals so far this season are running 2% less than last year at this time and 16% less than normal.

Precipitation. Mostly dry weather prevailed for the first one-half of the month with a statewide average of 1.30 inches of rain (normal for the period of 2.22 inches). However, locally heavy rains of four inches or more occurred on the night of the 8th in parts of central Iowa and the southwest corner of the state where Sidney received 5.75 inches. Much heavier rains fell during the second one-half of the month with a statewide average of 4.10 inches, or more than double the normal for the period of 1.98 inches. The bulk of the rain during this late month period arrived on the 17th-18th and 27th-28th. The first of these two events brought torrential rain to a wide area of northwest Iowa with 8.33 inches falling at Cherokee. Heaviest rains with the second event fell across central Iowa with the largest official total of 6.59 inches at Steamboat Rock while unofficial totals of nearly ten inches were reported over parts of southeast Webster County and southern Hamilton County. However, the month's heavy rain events were largely confined to central Iowa and the western one-third of the state. Most of eastern Iowa saw below normal rainfall for the month. August rain totals varied from only 1.14 inches at Keosauqua to 13.02 inches at Randolph.

Summer Summary. Temperatures during the three summer months averaged 70.3° or 1.3° below normal while precipitation totaled 17.62 inches or 3.91 inches above normal. This ranks as the 29th coolest and 7th wettest summer among 143 years of records. However, a cooler and wetter summer was recorded just last year when Iowa recorded its fifth coolest July and third wettest June.

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

                 __________2015__________________________2014____
                 AUG  JUL  JUN  MAY  APR  MAR  FEB  JAN  DEC  NOV
Maximum High:     25   22   69   28   34  182   13  113   84   24
Minimum High:    269  261   88  316   28  102  364   65   60  634
Maximum Low:      38   54   32   82   34   29   25  135  451    5
Minimum Low:     156  139   26   87   76   98  345  111   28  550
Maximum Precip:  158  214  151  155  122   17  113   67  121   67

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

                      2015
                 AUG   JUL   JUN   MAY   APR   MAR   FEB   JAN
High Temp Bias   0.1   0.0   0.0  -0.1   0.0   0.3   0.3   0.2
High Temp STD    1.8   1.7   1.7   2.5   2.2   2.6   2.8   2.5
Low  Temp Bias   0.2   0.2   0.2   0.1   0.3   0.4   0.3   0.1
Low  Temp STD    2.1   2.0   2.0   2.0   2.7   2.9   2.9   2.6
Precip    Bias  -0.01  0.00  0.00 -0.01  0.00  0.01 -0.16  0.01
Precip    STD    0.27  0.29  0.33  0.20  0.13  0.13  0.05  0.04