Iowa Monthly Climate Summary – June 2016

Temperatures

The statewide monthly average temperature was 73.2°F or 3.5°F above normal (See Figure 1). June 2016 ranks as the 14^th warmest June among 144 years of statewide climate records. A warmer June was last recorded in 1991. The average temperature at Des Moines and Waterloo was 77.3°F and 71.9°F respectively.  Des Moines was 5.5°F above normal while Waterloo was only 1.9°F above its monthly average. On the 15^th, the hottest temperature of 96°F was recorded for the month at Des Moines while the coldest temperature was 56°F on the 2^nd. The hottest temperature at Waterloo was 95°F on the 10^th while just two days earlier the low temperature dropped to 46°F.

Above normal temperatures prevailed for the majority of month of June across the state. A long hot spell occurred from the 9^th to the 20^th when the hottest temperature of 100°F was recorded at Little Sioux on the 11^th (See Figure 2). This 100°F ended up being the hottest temperature for the entire state during June 2016 and was Iowa’s first triple-digit temperature since September 10, 2013. The state’s second longest streak without a 100°F reading ended on the 11^th with 1,004 consecutive days. The longest streak is 1,438 consecutive days from August 3, 1991 to July 9, 1995.  The maximum temperature at Des Moines from the 9^th to the 27^th was 85°F or higher for 19 consecutive days in June.  This became the longest streak of its kind during the month of June since 1878 at Des Moines. The previous longest stretch was 17 consecutive days set in June 1956.

Precipitation

The statewide average precipitation was 3.69 inches which was 1.33 inches below the state’s normal for June (See Figures 3 & 4). This ranks as the 45^th driest June out of 144 years of statewide climate records. The monthly totals at Des Moines and Waterloo were 1.47” or 3.47” below normal and 8.97” or 4.98” above normal. Des Moines recorded its 10^th driest June since 1878 and Waterloo recorded its 4^th wettest June since 1895. This was common throughout the state as the precipitation was highly variable (See Figure 5). For example, Cedar Falls had a whopping 11.22” while Salem only recorded 0.25” for the entire month. By the end of the month, much of south central to southeast Iowa were placed into Moderate Drought by the U.S. Drought Monitor with much of the southwest to western part of the state classified as Abnormally Dry (See Figure 6). Severe weather was limited throughout the month of June, even though June is Iowa’s peak severe weather month. In fact, the first half of 2016 was fairly “quiet” with respect to severe weather (See Figures 7a/7b).  The most active day came on June 14^th when several central to northern Iowa counties reported wind damage. Heavy rain and damaging winds plagued a few counties during the evening of the 25^th into the early morning on 26^th (See Figure 8). Flooding was also limited during the month with only 1 river reaching flood stage and just a handful of Flash Flood Warnings issued by National Weather Service Office in Des Moines.

The U.S. Drought Monitor issued on June 28, 2016 placed Moderate Drought over south-central to southeast portions of Iowa and Abnormally Dry conditions over central to western Iowa.

Heavy rain fell over southwest to east-central Iowa during the overnight hours from the 25th to the 26th. 24-hour precipitation ending at 7 AM CDT June 26, 2016.

Year-to-Date NWS Severe Thunderstorm Warnings ending on June 29, 2016. NWS Des Moines only issued 60 Severe Thunderstorm Warnings, but from 2005 to 2015, NWS Des Moines averaged 292 Severe Thunderstorm Warnings per season. Image Courtesy of Iowa Environmental Mesonet.

Year-to-Date NWS Tornado Warnings ending on June 29, 2016. NWS Des Moines had only issued 4 tornado warnings up until that point. Image is courtesy Iowa Environmental Mesonet.

Blog post by Kenny Podrazik, Meteorologist, NWS Des Moines