Numerical weather models are indicating the potential for frost (29-32°F) or hard freeze conditions (below 28°F) to develop across the northern Corn Belt Sept. 14-16. The models have been consistent with a cold air push for the past three days which gives a high degree of confidence that the event will occur, according to Al Dutcher, University of Nebraska Extension state climatologist.  

For the morning of Sept. 15: hard freeze conditions for northeastern Minnesota, the northern half of Wisconsin, and the northern peninsula and northern half of the southern peninsula of Michigan. Scattered frost to freeze conditions are currently projected for extreme eastern North Dakota southeastward through southern Michigan.

For the morning of Sept. 16: scattered frost to freeze conditions for most of Michigan, northern Ohio, northern New York, and northern Pennsylvania. Hard freeze conditions are projected for southeastern Ontario - most of the agricultural grain crops are grown in this Canadian province.

Because of the spring planting delays due to excessive moisture and below normal May temperatures, a considerable amount of acreage in the frost/freeze forecast area has not reached physiological maturity. Many of these areas need normal temperatures into early October to escape significant damage.

Even if the freeze doesn't occur, crop maturity will grind to a halt as daily highs from Sept. 14 to Sept. 22 will struggle to reach the lower 60s.

Source: University of Nebraska