A new UNL Yield Forecast came out last Friday. The high probability of near- or above-average yields continues at all Iowa locations. The Sutherland and Kanawha locations still have considerable probability of below normal yields. The Lewis location has greater than a 99% probability of exceeding the long term yields. There is still are wide range of yield potentials but that range decreased from previous forecasts. The range of yield potentials forecast is still large due to only being roughly halfway through grain fill.
Probability of an early-killing frost is likely (>50%) in in northern IA locations, especially for crops that have fallen behind in development. It is very likely that maturity will be reached in central and southern Iowa before a killing frost.
Both the maximum and minimum temperatures are below normal for all locations. Solar radiation has been average to below average at 5 of 6 locations. This combination has slowed development of the crop and will likely delay maturity.
It should be noted that this forecast does not take into consideration stand establishment issues, hail, flooding, replant situations, disease/insect incidence, or nitrate leaching. Additional yield forecast information from Iowa and the other 9 states can be found at; https://cropwatch.unl.edu/2015-forecasted-corn-yields-based-sept-2-hybrid-maize-simulations.