When Can U.S. Corn Growers Expect First Frost?

At this point, we need to talk frost dates. 

All eyes are still on yield and acreage estimates for corn, especially after the USDA’s latest WASDE report painted a strong production forecast. Given the stretch of flooding and wet weather that started the year, and the hot and dry weather that followed, that forecast for decent yields at the end of the season can be considered generous at best.

When there’s late planting, there needs to be a conversation about the first frost. Between corn’s silking – its crucial reproduction period – and its maturity – also known as “black layer” – there are about fifty five days. That’s usually more than enough time. In a season where rain and flooding kept farmers from getting their crops in the ground until July, that countdown has to be the metric on everyone’s mind.

I. First frost: a moving target with devastating implications. 

Crop progress caught up with a favorable stretch of weather through the end of July and into the beginning of August. Whether or not is enough is all dependent on that time when the crop stops growing. It is far from certain that this crop would make it to the end – which could cut into the current yield estimates. 

II. What are the forecasts today?

Shifting weather patterns now put U.S. growers on track to expect a more average first freeze, compared to predictions that came earlier in the season for a relatively early first freeze.

III. What’s our exposure if there’s an early frost? 

Up to two billion bushels of corn could be at risk if an early freeze barrels in to the U.S., which represents anywhere from ten to fifteen percent of the total production. While some of these bushels will eventually be harvested for silage – particularly in key dairy states like Wisconsin and Michigan – there are, at best, many hundreds of millions of bushels at risk. In a scenario where counties experience a median hard freeze (e.g., a freeze that would have occurred in five of the past ten years) a billion or more bushels are at risk.  

When corn is frozen before physiological maturity, the harvested grain will be of poor quality and have very low test weights.

Methodology note: an early freeze constitutes a hard freeze of 28°F, which would have occurred in at least one place in each county in 1 of the past 10 years.  The median freeze scenario is a freeze that would have occurred in 5 of the past 10 years, and the late freeze scenario would have occurred in 8 of the past 10 years. This is not a 2019 weather forecast, and area by state is assumed to be the same as 2018.

IV. How can growers prepare?

If a grower anticipates that their corn will not reach maturity, it’s not a lost venture. A grower could harvest early for silage, a fodder product that can then be fed to either cattle or sheep, or even as biofuel feedstock. But how can growers make a decision that goes past the freeze date predictions coming across at either the national, or state level – a vantage point too high to have anything actionable? 

Through Indigo’s online “first freeze” calculator, growers can view the historical early, average, and late frost dates across more than 2,700 counties in the United States – as well as the date those counties would have needed to see silking in their corn crop in order for it to reach maturity. Find that map, below.


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