Across several states, climate change is fueling conditions that make watching the corn grow a nail-biter for farmers. Factors like consistently high summer overnight temperatures and heavier-than-usual rains at the wrong time can all disrupt the plants’ pollination -- making each full ear of corn less of a guarantee and more of a gamble.

Overall, corn growers got lucky this year with some late-season weather that contributed to what is now predicted to be a record bumper crop. But for farmers and experts alike, climate change is intensifying the waiting game during a critical time of year between planting and harvest.

Robb Rynd and his brother grew up farming and wanted to do more of it outside their day jobs, so they went in together on a little over 200 acres of corn, soybeans, wheat and sorghum. Last year was a good year, and Rynd said he enjoyed walking the fields with his kids to see how the corn was doing. This year, some of his crop has shown signs of pollination issues, including smaller cobs and patchy kernels.

Overall, corn growers got lucky this year with late-season weather that contributed to what is now predicted to be a record bumper crop. But experts say bouts of extreme weather are intensifying the waiting game during a critical time of year between planting and harvest. 

Human-caused climate change has worsened multiple U.S. extreme heat events this year and has steadily increased the likelihood of hotter overnight temperatures since 1970, according to Climate Central, an independent group of scientists who communicate climate science and data to the public.

As a corn plant grows, the leaves unroll to reveal the tassel, the part that sheds pollen, explained Mark Licht, an associate professor of agronomy and an extension cropping systems specialist at Iowa State University. If the plant grows too fast, which can happen when it's consistently very hot, the tassel may be wrapped too tightly by the leaf, meaning less pollen gets released. 

That can lead to patchy ears of corn. Tight tassel wrap was reported in pockets across parts of the Midwest and the Plains, according to some agricultural trade publication reports during the growing season.

High temperatures can stress corn in other ways, lowering pollen production, reducing pollen's viability or drying out other parts of the plants, reducing fertility.

This winter, the U.S. drought monitor reported drought in nearly 60% of corn production areas in the Midwest. But near or above normal rainfall nearly everywhere east of the Rockies this summer brought that down to just 3% as of the beginning of August, said Brad Rippey, a meteorologist with the U.S. Department of Agriculture.

Late summer is a make-or-break time for farmers: They're trying to gauge how much they'll make from the year's crop and planning their next steps, and patchy pollination doesn't help.

When the uncertain pollination is at its worst, if 15% to 25% of every ear of corn doesn't have kernels, that could mean a significant yield loss over a large field, said Nicolle Ritchie, a Michigan State University extension agent who helps Walton and Rynd survey their crops.

(AP Video by Joshua A. Bickel)