The quality controlled Iowa COOP data for June 2017 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 71.2° or 1.5° above normal while precipitation totaled 3.54 inches or 1.48 inches less than normal.   This ranks as the 23rd warmest and 38th driest June among 145 years of records.   A lower June rain total was last recorded in 2012 while June of 2016 averaged 1.9° warmer.

Temperatures. An unseasonably cool period prevailing for the two weeks from May 18th to June 1st came to an abrupt end on June 2nd when a string of sixteen consecutive warmer than normal days began.   Temperatures averaged more than ten degrees above normal on the 3rd - 4th and 10th – 13th.   Daytime highs in the nineties were recorded somewhere in Iowa every day from the 2nd through the 16th.   A welcome respite from the hot weather began late on the 17th with only one day (22nd) bringing widespread hot weather for the remainder of the month.   Temperature extremes varied from highs of 97° at Little Sioux on the 13th, Lamoni on the 15th and Little Sioux on the 21st to lows of 40° at Cresco, Elkader and Grinnell on the 1st and again at Battle Creek and Grinnell on the morning of the 27th.

Cooling Degree Day Totals. Home air conditioning requirements, as estimated by cooling degree day totals, averaged 24% greater than normal but 16% less than seen during the very hot June of 2016.   Cooling degree day totals are running 13% more than normal so far in 2017, but 19% less than last year at this time.

Precipitation. A very dry weather pattern prevailed from May 28 through June 12 with a statewide average of only one-tenth of an inch of rain falling compared to a normal for the period of 2.47 inches.  Rain fell almost daily somewhere in the state for the remainder of June but rain amounts and areal coverage were frequently limited.   Monthly rain totals were below normal over the southwest two-thirds of Iowa with the exception of the far southwest corner.   Lowest totals were over the far southeast where Fairfield (0.88), Donnellson (0.91 inches) and Ottumwa Airport (0.97) recorded under an inch of rain in what is usually the most reliable month of the year for rainfall.   At Ottumwa this was the third driest June among 130 years of records (1911: 0.24”; 1992: 0.78”; 1913: 0.90”).   At Fairfield it is the fifth lowest June total among 137 years of records (lowest June total since 1963).   Finally, at Donnellson this ranks as the third lowest June total among 76 years of record, with just last June being drier with 0.53 inches.   On the other extreme very wet conditions prevailed over portions of north central and northeast Iowa.   New Hampton was the wet spot with 9.79 inches of rain where there were four dates during the second one-half of the month with 1.5 inches or more of rain.

Severe Weather. Severe thunderstorms were reported somewhere in the state on twelve dates during the month with the bulk of the activity coming on the 15th (26 counties impacted), 28th (27 counties) and 29th (21 counties).   The National Weather Service (NWS) confirmed 13 tornadoes on the afternoon and evening of the 28th with greatest damage reported at Prairieburg in Linn County.

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

                 2017__________________________________2016______
                 JUN  MAY  APR  MAR  FEB  JAN  DEC  NOV  OCT  SEP
Maximum High:     28   36    5   92  546   43   40  226  242  225
Minimum High:      8  189  122   22    0   36   44   21    8   15
Maximum Low:      95   13   43   43  154  367   70  125  184  338
Minimum Low:      59    5   12   42    0   23   99   15    6    4
Maximum Precip:   35   39   97   40   55  219  167   85  118  295

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

                 2017                                   2016      
                 JUN   MAY   APR   MAR   FEB   JAN   DEC   NOV   OCT
High Temp Bias   0.1  -0.2  -0.3  -1.0  -0.9   0.2   0.3   0.2   0.1
High Temp STD    M     M     M     M     M     2.0   2.0   2.1   2.2
Low  Temp Bias   0.1  -0.2  -0.3  -0.4  -0.2   0.0   0.1   0.0   0.2
Low  Temp STD    M     M     M     M     M     2.3   2.3   2.8   2.5
Precip    Bias   0.08  0.07  0.02  0.05  0.05  0.01 -0.02  0.00  0.00
Precip    STD    0.66  0.42  0.49  0.39  0.33  0.07  0.07  0.09  0.12

The standard deviations are missing this month due to some new code that is not behaving as I expected. Just haven't allocated time to figure out why yet, sorry.