Growing degree days (GDD), also known as heat units, are calculated by taking the average of the high and low temperature in a day, minus the base temperature of 50°F. The optimal number of growing degree days varies depending on the crop and maturity. Tracking growing degree days is not only helpful in monitoring your crop progress throughout the growing season, but it can also be used in determining when certain insects are more likely to occur. As you can see in the graph below, Des Moines, Red Oak, and Fairfield have accumulated more growing degree days so far this year than the northern part of the state. Most locations shown are accumulating GDDs at a rate similar to the past few years.
The map below shows the cumulative precipitation beginning in April for several locations across the state. Red Oak and Charles City currently have the highest total, while Cherokee is estimated to have the least cumulative rainfall since April 1 out of these locations. As you can see, most of the state went from the end of May to the middle of June without any significant rainfall events, so the more recent rains across the state have been much needed.