Summer precipitation summary
Since June 1st, the wettest parts of Iowa have received around 20 inches of rain. The rainiest areas in the state include central Iowa, primarily Story and Boone Counties, and north-central Iowa, Winnebago and Worth Counties. Some of the driest areas include the Johnson-Linn County line, where they have received almost 7 inches of rain, southwest Iowa, where almost 10 inches of rain has fallen, and northeast Iowa, where almost 9 inches of rain has fallen. Almost all of the state has received above normal rainfall since June 1.
Despite these areas receiving less than half of the rain compared to other areas of the state, all 9 climate districts reached their top 30 rank for wettest July since 1893. The north central climate district ranked number one wettest for July, and the central climate district ranked number 2. Preliminary storm reports from the Storm Prediction Center for the month of July show 14 tornado and 6 severe hail reports.
Heat and humidity
Both daily high and low temperatures were generally above average during July in Ames. Since June 1st, average temperatures have been slightly warmer than normal. The second half of June is when the summer heat started kicking in. Despite a few mild days, most of July has also been warmer than normal. Dew point temperatures in June and July have stayed mostly between 60-80 degrees. According to an article by the National Weather Service, dew point temperatures greater than 65 degrees indicate a lot of moisture in the air and can feel quite oppressive.
Most of the moisture in the air in Iowa during the summer comes from large-scale moisture transport from the Gulf. Winds in central Iowa since June 1st primarily came from the south and southeast. These winds were also strong, between 10-20 miles per hour.
Agricultural implications
High rainfall totals have led to drought removal for most of the state. A few counties in southern Iowa still have remnants of abnormal dryness to moderate drought. Much of the rest of the state has ample soil moisture, with potential ponding in low-lying areas. The storm system that moved through the state on July 28-29 resulted in some crop damage. The greatest agricultural concerns from this storm are lodged corn and soybeans, and ponding in fields. Despite these concerns, crop condition reports from the USDA show Iowa has the highest percentage of good to excellent corn in the Midwest.
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- Weather and Climate Extension Specialist