By Harry Hillaker, State Climatologist, Iowa Department of Agriculture & Land Stewardship
The past reporting week began with very hot weather on Monday (23rd), Tuesday (24th) and Wednesday (25th) with triple digit heat being widespread across the southern two-thirds of Iowa. The heat subsided somewhat on Thursday (26th) with readings falling a little below normal in many areas on Friday (27th) and over most of the state on Saturday (28th). Eastern Iowa enjoyed one more day of milder weather on Sunday (29th) but temperatures in the low to mid 90s returned to the southwest. Temperature extremes for the week ranged from Monday afternoon highs of 107 degrees at Donnellson, Fairfield and Keokuk to a Saturday morning low of 53 degrees at Manchester. The 107 degrees temperatures on Monday were the highest official readings recorded in Iowa since Keosauqua reached 107 on July 29, 1999. Temperatures for the week as a whole averaged 5.9 degrees above normal. Thunderstorms were widespread on Wednesday night and again from Saturday morning into Sunday morning. The heaviest rains on Wednesday night of one to two inches were mainly restricted to a small part of far southwest Iowa and over several northeastern counties centered near Waterloo-Cedar Falls. The weekend rains were greatest over a small area of northwestern Iowa where an inch or more fell from near Spencer to near Fort Dodge. Most of Iowa saw some rain during the week, however, locations such as Atlantic, Audubon, Harlan and Guthrie Center were left dry. At Audubon there have now been 36 consecutive days without measurable (0.01 inch or more) rainfall. Greatest rain totals for the week were recorded at Traer (Tama Co.) with 2.78 inches and the Oelwein Airport with 2.89 inches. The statewide average precipitation was 0.70 inches while normal for the week is 0.96 inches. This was the wettest week in five weeks yet was also the 11th week of the past 12 with less than usual rainfall. While the rain was very welcome, Wednesday night’s storms were accompanied by severe weather with high winds and/or large hail reported from 34 counties. Preliminary data indicate that July 2012 will likely go into the record books as the third hottest and fifth driest July among 140 years of state records.