The quality controlled Iowa COOP data for June 2016 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. Iowa temperatures averaged 73.1° or 3.4° above normal while precipitation totaled 3.70 inches or 1.32 inches less than normal.   This ranks as the 15th warmest and 45th driest June among 144 years of record.   A warmer June was last recorded in 1991 and a drier one in 2012.

Temperatures. Warmer than normal weather was the rule through most of June.   While the daily statewide average temperature was slightly below normal on seven days during the month there was not a single day when every Iowa major reporting station was cooler than normal.   The warmth was most firmly established during the middle of the month with above normal temperatures throughout Iowa every day from the 9th through the 20th.   Little Sioux was the hot spot with a 100° maximum on the 11th.   This was Iowa’s first triple-digit reading since September 10, 2013.   This ended the second longest streak without 100° temperatures in Iowa at 1,004 consecutive days (record longest is 1,438 consecutive days from August 3, 1991 through July 9, 1995).   The relative lack of 100 degree temperatures in recent years is tied to frequent wetter than normal summers in Iowa.   The heat was most pronounced in southwestern Iowa where Little Sioux recorded 17 days with maximum temperatures of 90° or higher.   On the other extreme Allison, Anamosa, Dubuque, Elkader, Fayette, Forest City, New Hampton and Osage reached or exceeded 90 only once.   Belle Plaine, Elkader and Grinnell recorded the month’s lowest temperature with 43° readings on the morning of the 8th.

Cooling Degree Days. Home air conditioning requirements, as estimated by cooling degree day totals, averaged 59% greater than last June and 48% more than normal.   Thus far this air conditioning season cooling degree day totals are running 57% greater than last year at this time and 39% greater than normal.

Precipitation. June rain amounts were highly variable across Iowa.   Rainfall was much more frequent and came in greater amounts over about the northeast one-third of the state where monthly totals were as much as twice the June normal.   Cedar Falls reported the most rain with 11.22 inches while Salem in Henry County recorded only 0.25 inches.   At Donnellson in Lee County their June rain total of 0.53 inches is second only to 1991’s 0.45 inch total among 75 years of records.   At month’s end a large portion of south central and southeast Iowa was classified in ‘moderate drought’ by the U. S. Drought Monitor with an ‘abnormally dry’ designation for much of west central, central and southwest Iowa.

Severe Weather. As has been the case all year, severe weather was not as frequent or as widespread as typical across Iowa in June.   The most widespread event generated severe storm reports, mostly high winds, from 15 central and northern Iowa counties on the evening of the 14th.    However, the most damaging storms hit northwestern Iowa where a combination of hail and high winds resulted in considerable crop damage on the evening of the 17th.

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

                 2016________________________________2015________
                 JUN  MAY  APR  MAR  FEB  JAN  DEC  NOV  OCT  SEP
Maximum High:    238   65   84  135  213   29  244   85   75  130
Minimum High:     17   81   72    5   59   98   13   56   21   13
Maximum Low:     196   21   63  268  159   89  467  171   79  336
Minimum Low:      42   72   53   10   19   63    5   58   20   25
Maximum Precip:   84   92   72  124  141  156  439  316  162  150

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

                 2016                                2015
                 JUN   MAY   APR   MAR   FEB   JAN   DEC   NOV   OCT
High Temp Bias   0.2  -0.1   0.2   0.4   0.6   0.3   0.2   0.3   0.2
High Temp STD    2.1   2.0   2.5   2.6   2.4   2.1   2.0   2.2   1.8
Low  Temp Bias   0.2   0.2   0.2   0.3   0.2   0.2   0.1   0.2   0.1
Low  Temp STD    2.3   2.5   2.4   2.7   2.4   2.5   2.2   2.7   2.6
Precip    Bias  -0.02  0.00  0.00  0.00  0.01 -0.01 -0.01 -0.00 -0.01
Precip    STD    0.25  0.17  0.11  0.09  0.07  0.27  0.14  0.14  0.08