Kevin Marcus of Marcus Weather Consulting gives the areas to watch as harvest goes into the home stretch in the northern hemisphere and the growing season is shaping up in the southern hemisphere.
Looking at the U.S., South American and Chinese weather patterns, here are his takeaways on the impact and outlook of weather:
U.S. harvest season is a mirror of 2024 in many ways.
Marcus says for many in the Midwest, September and October are echoing patterns this time last year being warmer and dryer than average.
He notes two earlier weather patterns in the year are bringing attention to their impact on yields.
In the eastern corn belt, the prolonged heat may have dinged yields.
“We had lots of warm night sin July and August,” he says. “For some, it was the highest numbers since 2010 and 2011.”
When nighttime temperatures remain elevated, the respiration steals from grain development resulting in shallower kernels.
In the western corn belt, the focus is on the favorable conditions for disease—including the expansion of southern rust.
“We’re seeing southern rust stealing 40 to 50 bu/acre in fields that were left untreated,” Marcus says. “Iowa was the epicenter of the problem, and if just 10% of the fields weren’t sprayed properly at a 50 bu loss, that’s 5 bu. off the state yield. And 1 bu. off the national yield.”
You can hear more about his weather analysis and the effect on yield estimates here:
La Nina is a factor.
Marcus is watching the development of La Nina, warmer waters in the eastern Indian ocean and systems and patterns developing in southeast Asia. He says it all adds up to polar jet getting invigorated.
As such, he sees “more of a slug” for the finishing weeks of corn harvest across the Midwest.
And this winter, especially compared to last year, he sees wet heavy snow across the northern plains starting in November.
Questionable start for the southern hemisphere.
As Brazil and Argentina’s growing seasons get kicked off, there’s cooler and less wet weather.
“This isn’t typical. It usually rains every other day. Now it’s only raining once a week. And temperatures are popping above 100 degree. Young crops are being stressed early,” Marcus says.
Looking ahead, he notes there aren’t any “red flags” for the weather dramatically effecting yields, but there is definitely risk in the forecast.
China’s domestic production is a question mark.
Marcus says a developing story to watch are yields for the Chinese corn crop.
“We just came through seven weeks of exceptional rain in the north China plains,” he says. “When corn can’t be harvested, and you’re getting rains every other day for seven weeks, you have an idea of what that quality will look like.”
When a comparable weather pattern occurred in 2022, Marcus points to private estimates stating a loss of 30 million metric tons.
