I often wondered if corn and soybean crops can affect weather in late summer?
—David Vondra Davis, Illinois
They certainly do. Moisture from plants is returned to the atmosphere in a process called evapotranspiration. During the peak of the growing season, 2.5 acres of corn can add about 9,000 gallons of water to the atmosphere in a 24-hour period. Considering the planted acreage in the Midwest, a huge amount of moisture is added to the air. The National Weather Service deployed automated weather stations in the 1990s, many in agricultural areas, and forecasters noticed dew point temps often 5 to 8 degrees higher than readings at airport locations. (Note an 86 dew point at Monticello, IA on 8/10/21). First thought to be erroneous, studies concluded these higher dew point readings were correct, a result of proximity to cropland.