Written by Theresa Rose on June 12, 2018

By Dr. Justin Glisan, State Climatologist, Iowa Department of Agriculture and Land Stewardship

The week began with warmer temperatures across northern Iowa, ranging from 2-7 degrees above normal. With the exception of the southwest corner, where average temperatures were 2-3 degrees cooler than expected, the rest of Iowa had near normal values in the upper 70s. On the 4th, Swea City (Kossuth County) reported a high of 91 degrees. Sioux City observed a high of 94 degrees, 15 degrees above average on the 5th. Mid-week through the weekend saw above average temperatures across most of Iowa; 95 degrees was observed in Rock Rapids (6th) and Little Sioux (7th). Lamoni ended the week with a high of 93 degrees. Between the 4th and the 5th, the state was dry, with only a few reports of measurable precipitation from pop-up thunderstorms. Guttenberg recorded 0.2 inches on the 4th; Dubuque observed 0.05 inches (5th). An organized line of storms moved between Mason City and Des Moines on the morning of the 6th. Quarter size hail was reported in Buchanan County. Widespread convective activity in the afternoon and evening brought heavy rain, hail and straight-line winds to east central Iowa. Ames received 1.41 inches of rain along with dime to quarter size hail; Stanhope reported golf ball size hail. Overall, there were more than 50 reports of severe hail and high winds. Thunderstorms brought above normal amounts of rain, around 0.2 – 0.4 inches, to central Iowa mid-week. From the 7th to the 10th, flooding occurred in northeastern Iowa, including Mitchell and Floyd Counties, as slow moving thunderstorms produced multiple inches of rain. Iowa’s southern third reported measurable rainfall on Sunday, as a line of thunderstorms slowly progressed across the region. Forest City reported a brief touch down of a rope tornado on the 9th. Slow moving storms in northeastern Iowa also produced flash flooding in multiple locations on the 10th.