Quality of stored grain must be maintained through the entire summer period, until stocks can be rotated in the fall. Summer storage is challenging because warm temperatures and high relative humidities put even dry grain at risk for mold and insect activity. Relative humidities in the last two weeks have been very high.
The chart below explains why summer aeration can create either continued mold growth or excessive moisture shrink (below 14% moisture corn; 12% moisture soybeans). The horizontal lines are the market standard moistures for corn and soybeans (15% and 13% respectively).
Aeration in the fall is not likely to create overdry grain. Market moisture grain is not likely to spoil if steady fall conditions are maintained. However, in summer, even dry grain can spoil. Aeration in summer creates further drying and moisture shrink, and if the humidity is high, spoilage will continue.
Wet grain in storage now has probably used up its shelf life. It should be marketed quickly. Elevators and processors report that average condition of inbound corn is declining; there are still almost two warm weather months remaining to reach the 2015 crop.
(Source – http://www.farms.com/news/pay-attention-to-condition-of-stored-corn-95613.aspx)