Super El Niño 2026 Has Grain Markets on Edge. Which Climate Indices Show the Largest Historical Correlations with July Corn and Soybean Weather?

Background: The grain market is currently focused on El Niño and the potential for historic ENSO values in 2026. With forecasters signaling a high probability of El Niño conditions during the summer growing season, market attention has centered on ENSO as the primary climate driver of July corn and soybean weather.

But: The historical record shows that Relative Niño 3.4 — the standard ENSO benchmark does not show as large a historical association with July weather across U.S. corn and soybean production regions as the current market discussion suggests.

This analysis examines historical Pearson correlations between a broad set of climate indices and July observed weather across U.S. corn and soybean production regions. Here is what the data shows.

Why El Niño Is Dominating the 2026 Grain Market Outlook

As of May 2026, forecasters are assigning a high probability to El Niño conditions developing during the summer growing season. Some models are projecting values comparable to the 1982, 1997, and 2015 events. Agricultural market commentary and seasonal outlooks have focused on the potential implications for Corn Belt temperature and precipitation in July — the critical pollination window for corn.

The market narrative: historic El Niño values mean elevated weather risk for U.S. corn and soybean production in July 2026. Notably, the three most recent high-magnitude El Niño events (1997, 2015, 2023) were each followed by record U.S. corn yields. Historical research has not identified a consistent relationship between ENSO intensity and Corn Belt summer weather outcomes.

Does the Prior Winter’s El Niño Foreshadow July Corn Belt Weather?

The most forward-looking version of the El Niño question is whether the winter ENSO state — largely known by spring — carries any signal for the following July. To test this directly, we paired the prior-winter (December–February) average of Relative Niño 3.4 with that same year’s July weather across U.S. corn production regions, over 45 seasons.

Figure 1: U.S. corn July precipitation (% of normal) by prior-winter (DJF) ENSO phase, shown as the phase mean with its 95% confidence interval. The number of years in each phase is labeled. The intervals overlap heavily.

 

 

The differences between phases are not statistically significant. Across the five phases the ANOVA and Kruskal–Wallis tests do not reach the conventional threshold (Kruskal–Wallis p ~ 0.06 for corn). The clearest tendency is in precipitation: July rainfall averages about 82% of normal following La Niña winters and about 110% following strong El Niño winters, but the difference between warm-winter and cold-winter years — about 11% of normal — is not statistically significant (Welch p ~ 0.25). Expressed as a single correlation, the prior-winter Relative Niño 3.4 explains very little of the variance in July precipitation (r ~ +0.20, p ~ 0.18). For temperature, the prior-winter ENSO state shows no statistically significant relationship with July maximum or minimum temperature, and the soybean-belt result is nearly identical.

In short, even the prior winter’s El Niño state — the information the market has in hand heading into spring — is a weak and statistically insignificant guide to July Corn Belt weather.

What Does the Historical Record Show for Relative Niño 3.4 and July Corn Belt Weather?

Relative Niño 3.4 is the index most directly tied to the El Niño narrative in grain market commentary. Below are its historical Pearson correlations with concurrent July observed weather across U.S. corn production regions.

 

Relative Niño 3.4 shows a near-zero historical association with July precipitation (r = +0.01) and modest associations with July maximum and minimum temperature across U.S. corn and soybean production regions. Of all the indices included in this analysis, Relative Niño 3.4 shows the lowest mean |r| at 0.09.

Which Climate Indices Show the Largest Historical Correlations with July Corn Belt Temperature?

July Maximum Temperature (Tmax)

Figure 2: Monthly July Tmax in U.S. corn production regions vs. top-ranked climate indices. Pearson r and slope annotated in each panel. Relative Niño 3.4 shown in the bottom-right panel for reference.

 

 

July Minimum Temperature (Tmin)

Figure 3: Monthly July Tmin in U.S. corn production regions vs. top-ranked climate indices.

Which Climate Indices Show the Largest Historical Correlations with July Corn Belt Precipitation?

July Precipitation (% of Normal)

Figure 4: Monthly July precipitation (% of normal) in U.S. corn production regions vs. top-ranked climate indices.

 

Among ENSO-related indices, El Niño Modoki and Niño 4 — which represent warm pool anomalies in the far western equatorial Pacific, not the traditional Niño 3.4 region — show larger precipitation associations than Relative Niño 3.4.

Overall Ranking: Mean |r| Across July Tmax, Tmin, and Precipitation

What Are the ABNA, NPM, and EPO?

These are extratropical and mid-latitude atmospheric circulation indices. They receive considerably less attention in grain market commentary than ENSO benchmarks, but show larger historical correlations with July Corn Belt weather in this analysis.

• ABNA (Asian-Bering-North American): A large-scale 500-hPa geopotential-height teleconnection extending from North Asia across the Bering region into North America (Yu et al., 2017). In this record, a positive phase is associated with anomalously warm July maximum and minimum temperatures across the Corn Belt.
• NPM (North Pacific Mode): A pattern of sea-surface-temperature variability in the North Pacific. In this record, a warm NPM phase is associated with suppressed July maximum temperatures and above-normal July precipitation across U.S. corn and soybean regions.
• EPO (Eastern Pacific Oscillation): A mid-latitude North Pacific circulation pattern that influences North American weather. In this record, a positive EPO phase is associated with warmer and drier July conditions across the Corn Belt.

These relationships are correlational and concurrent (July index versus July weather); they describe historical co-variability, not forecast skill or causation.

Frequently Asked Questions

Does El Niño cause drought in the Corn Belt in July?

The historical Pearson correlation between Relative Niño 3.4 and July precipitation across U.S. corn and soybean production regions is r = +0.01. The historical record does not show a notable association between Relative Niño 3.4 and July Corn Belt precipitation.

Does the prior winter’s El Niño predict July Corn Belt weather?

Pairing the prior-winter (DJF) Relative Niño 3.4 with the following July shows no statistically significant relationship with corn-belt precipitation or temperature. July rainfall tends to be modestly drier after La Niña winters (about 82% of normal) and wetter after strong El Niño winters (about 110%), but the differences are not statistically significant (Kruskal–Wallis p ~ 0.06).

What climate indices show the largest historical correlations with July Corn Belt temperature?

ABNA (Asian-Bering-North American), NPM (North Pacific Mode), and EPO (Eastern Pacific Oscillation) show the largest |r| values for July maximum and minimum temperature across U.S. corn and soybean production regions, based on historical Pearson correlation analysis.

Which ENSO index shows the largest historical correlation with July Corn Belt precipitation?

Among ENSO-related indices, El Niño Modoki (r = +0.20) and Niño 4 (r = +0.18) show larger historical associations with July precipitation than Relative Niño 3.4 (r = +0.01). These indices reflect warm pool anomalies in the far western equatorial Pacific.

Is a Super El Niño bad for U.S. corn yields?

The three most recent high-magnitude El Niño events (1997, 2015, 2023) were each followed by record U.S. corn yields. Historical research has not identified a consistent relationship between ENSO intensity and Corn Belt summer yield or weather outcomes.

What does this analysis suggest grain market participants should watch for July 2026?

Based on the historical correlation record, the indices with the largest |r| values for July Corn Belt temperature are ABNA, NPM, and EPO. For precipitation, NPM and EPO show the largest historical associations. Relative Niño 3.4 — whether measured in July or as the prior winter’s average — shows the lowest mean |r| of any index in this analysis.

Summary

The grain market is focused on El Niño and historic ENSO values ahead of the 2026 U.S. summer growing season. The historical record shows that Relative Niño 3.4 — the standard ENSO benchmark — has a near-zero historical association with July precipitation (r = +0.01) and modest associations with July temperature (r = -0.13 for Tmax, r = -0.14 for Tmin) across U.S. corn and soybean production regions. Extending the test to the prior winter’s (DJF) ENSO state — the information available to the market by spring — does not change the picture: it shows no statistically significant relationship with July corn-belt weather.

The indices with the largest historical |r| values for July Corn Belt weather are extratropical circulation patterns — ABNA, NPM, and EPO — with mean |r| values of 0.28 to 0.30 across temperature and precipitation variables. Relative Niño 3.4 shows a mean |r| of 0.09 — the lowest of any index in this analysis.

Methodology: Correlations are Pearson r between monthly climate-index values and July observed weather, weighted by U.S. corn production, for the U.S. aggregate region. The index–temperature and index–precipitation correlations are concurrent (July index versus July weather) and describe historical association, not forecast skill or causation. The prior-winter (DJF) analysis pairs the December–February Relative Niño 3.4 average with the following July across 45 seasons; per-phase samples are small (7–11 years). Analysis by Prescient Weather.