As outdoor temperatures begin to warm, the potential for grain storage problems increases.

With the likelihood for issues going up, the need for grain monitoring and management does as well, says Ken Hellevang, grain drying expert and retired North Dakota State University Extension agricultural engineer.

Navigating temperature changes

During a winter day, the outdoor air may fluctuate by 25 to 30 degrees Fahrenheit. This warms the bin and the grain next to the wall during the day, but they cool at night. The result is that the bin and grain near the bin wall will be near the average temperature. The same will occur during an extended warm period that is followed by a cool or cold period: the temperature will be near the average of the two periods.

Grain is an insulator, so grain temperature fluctuation is limited to the grain next to the bin wall. Dry grain that has been cooled to 20 to 30 degrees in northern regions is not expected to be affected by these temperature fluctuations.

“The stored grain temperature increases in parts of a bin in the spring due to solar heat gain on the bin,” says Hellevang.

Solar energy produces more than twice as much heat gain on the south wall of a bin in spring as it does during the summer. This, along with solar heat gain on a bin roof, can create an environment conducive to grain spoilage. A 10-degree temperature increase reduces the allowable storage time of grain by about half. For example, the storage time of corn at 17% moisture is reduced from about 130 days at 50 degrees to about 75 days at 60 degrees, and further, only 45 days at 70 degrees.

If the stored grain is dry, Hellevang recommends periodically running aeration fans in the spring to keep the grain below 40 degrees as long as possible through the beginning of summer. In northern states, night air is normally near or below 30 degrees in April and 40 degrees in May.

Frost and ice can block bin vents when the fan is operated at temperatures near or below freezing, which may lead to roof damage. Leave the fill and access door open as a pressure relief valve when operating the fan at temperatures near or below freezing.

Cover the fan when it is not operating to prevent warm air from blowing into the bin or being drawn in by a chimney effect, which could heat the stored grain to temperatures more prone to spoilage and insect infestations.

Hellevang also recommends ventilating the top of the bin to remove the solar heat gain that warms the grain. Providing air inlets near the eaves and exhausts near the peak allows the top of the bin to ventilate due to the warm air rising — similar to what occurs in an attic — as does a roof exhaust fan.

Monitoring grain moisture, temperature

Stored grain should be monitored closely to detect storage problems early, advises Rob Proulx, NDSU Extension ag technology and grain systems specialist. Grain temperature should be checked every two weeks during the spring and summer, as a temperature increase may indicate a storage problem.

Grain should also be examined for insect infestations. Checking the moisture content of stored grain determines if it needs to be dried. Proulx recommends verifying that the moisture content measured by the meter has been adjusted for grain temperature.

“Verify the accuracy of the measurement by warming the grain sample to room temperature in a sealed plastic bag before measuring the moisture content,” says Proulx. “Remember, moisture measurements of grain at temperatures below about 40 degrees may not be accurate.”

Some in-bin cables estimate grain moisture content by measuring temperature and air relative humidity, then calculating it using grain equilibrium moisture content equations. The measured moisture may differ by 1.0%-1.5% from the true moisture content, so Proulx advises verifying it with another moisture measurement method.

Corn needs to be dried to 13%-14% moisture for summer storage to prevent spoilage. Soybeans should be dried to 11%-12%, wheat to 13%, barley to 12% and oil sunflowers to 7%-8%. The allowable storage time for 13% moisture soybeans is less than 100 days at 70 degrees.

If grain stored in grain bags isn’t dry, it will spoil, and molds will grow. Grain in the bags will be at average outdoor temperatures, so grain will deteriorate rapidly as outdoor temperatures increase unless it is at the recommended summer storage moisture contents.

Grain bags that run east-west will have solar heating on the south side, creating a temperature variation that will move moisture to the north side. Continue to frequently monitor grain stored in bags.

In addition to storage practices, Hellevang stresses the importance of knowing the safety hazards associated with handling grain and applying recommended safety practices to decrease the risk of injury or death.

NDSU Agriculture Communication – Feb. 27, 2026

Source: Ken Hellevang, 701-231-7243, kenneth.hellevang@ndsu.edu

Source: Rob Proulx, 701-231-5389, rob.proulx@ndsu.edu

Editor: Dominic Erickson, 701-231-5546, dominic.erickson@ndsu.edu