What was a bullish forecast for the corn crop a few days ago has now been tempered by the possibility of an early frost.

Corn prices on the Chicago Board of Trade were up nearly the limit on Tuesday, as traders reacted to the weather news. The nearby futures contract settled at $3.465, up 28.75 cents from Monday.

New models from the National Weather Service show that on Sept. 25 the frost or freeze line could dip as far south as Tennessee.

To access the models for yourself, click here, then go down to GFS, the second row down. Pick the most recent forecast among the four choices: 00 UTC = midnight, 06 = 6 a.m. and so on. Click on “coarse” and it will take you to a time grid. Go one column over to where it says 850mb Temp. Then, pick how many days out you want to go. Under day 10, it may list 228 and 240, which refers to the number of hours from now. If you click on one of those, you will notice a blue line or isobar on the map that shows the predicted freeze line. 

A killing frost would cause corn plants to stop growing, thus keeping the ears from filling out any further.   

We will still have a big corn crop, as indicated by last Friday’s Crop Production report from USDA, according to Marty Foreman, senior economist with Doane Advisory Service in St. Louis, Mo. But the weather could temper things, he adds.

The USDA report said this year’s corn crop could total 13 billion bushels, the second largest on record.

Weather-forecasting is always an iffy proposition, especially when trying to do it eight to 10 days in advance. A lot can change in the interim. But forecast models from the National Weather Service show that a killing frost could occur in much of the Corn Belt from Sept. 23-26. In the article that appears above, we have provided a Web link to the National Weather Service forecast models so you can follow this yourself. Subjectively, it’s too early to have a frost. Whatever happened to global warming? — Tom Quaife, editor