What late-June sizzle could mean for US corn yields: Braun

Although the U.S. Corn Belt is in for a scorching weekend, June weather has been mostly supportive of crop development, with corn health ratings improving for three consecutive weeks.

But how much bearing might that have on final corn yields or weather outcomes for the pivotal month of July?

As early as last year, meteorologists warned that the U.S. Corn Belt could be due for drought in 2025, though that has yet to unfold. A mid- or late-summer drought could still be in the cards, of course, and the yield impacts would vary depending on timing.

Recently, new-crop CBOT corn futures appeared to be carrying minimal weather premium as prices sank to six-month lows this week. December corn (CZ25) has since bounced with this weekend’s hot forecast in focus, though prices remain well off the year’s peak.

WEATHER VERSUS YIELDS

Recent weather models suggest that both temperatures and precipitation for June will be above average across the Midwestern United States. While warm Junes are more likely to feature dry conditions, this warm-wet combination is similar to last year.

Corn yield outcomes have varied widely in relation to observed June weather. But July temperatures are where things start to separate.

In the past quarter-century, the worst corn yield outcomes all coincided with warmer-than-normal Midwestern Julys. The truly good years featured cool Julys, but slightly warm temperatures were also passable a couple of times (2016, 2017).

Big corn yields have resulted from abnormally dry Julys (2014), though this works only if July is cool and June and/or August rainfall is ample.

The strongest corn yields all resulted in years where July-August Midwestern rainfall was near or above normal. Near-average yields have coincided with dry July-Augusts, but only when July temperatures were cool.

Obviously, a hot July plus a dry July-August is the very worst combination for yields, which was seen in 2011 and 2012. Interestingly, 2011 is the last time that corn conditions improved over the same three weeks in June as the 2025 ones.

But the fact that June 2025 will likely feature above-average rainfall doesn’t tell us much about what’s coming next. July and August have been both wet and dry following wet Junes, though warm Julys are more likely to follow warm Junes.

Current extended forecasts suggest the next four weeks could be warmer than average across the central Corn Belt, featuring pockets of both wet and dry weather. Uncertainty is always high when it comes to long-range forecasts, but the current outlook should warrant some caution.

SOYBEANS VERSUS AUGUST

August matters for U.S. soybean yields like July matters for corn. Last year, the market was harshly reminded of the need for August rains to support large soybean yields.

August 2024 rainfall across the Midwest amounted to just 87% of normal, the driest August since 2013. But 2024 U.S. soybean yield forecasts were still easily at record levels as late as October.

The government’s yield estimate plunged 4.5% between October and January, the largest decline for that period since 1993, emphasizing the significance of the August rainfall deficit.

That occurred despite above-average June and July rains, meaning the range of possibilities for U.S. soybean yields is even wider than those for corn given that August is still several weeks away.

Karen Braun is a market analyst for Reuters. Views expressed above are her own.

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