Meteorologist Eric Snodgrass says shifting jet stream patterns, repeated storm systems and a strengthening El Niño could bring additional moisture challenges for harvest across the U.S. Midwest and parts of Canada through early October.
As summer gives way to autumn, farmers across the U.S. Midwest and parts of Canada are watching a weather pattern that appears poised to become increasingly active during the heart of harvest season.
According to Nutrien Ag Solutions meteorologist Eric Snodgrass, recent atmospheric changes suggest a departure from the persistent ridge of high pressure that has dominated portions of North America.
Instead, a more dynamic setup featuring both northern and southern jet stream branches could bring additional rainfall opportunities across major crop-producing regions through late September and early October.
The shift comes after a year marked by weather extremes. Snodgrass noted that 2026 has featured an unusually active severe weather season, with wind reports running well above average and significant contrasts between regions experiencing excessive rainfall and those struggling with drought.
For growers in key Corn Belt states, moisture has already been abundant. Areas spanning Kansas, Nebraska, Iowa, Minnesota, Wisconsin, northern Illinois and parts of Ohio have received exceptionally heavy rainfall in recent weeks. Some locations in eastern Iowa and central Ohio have recorded their wettest start to September on record.
Those conditions have created a growing concern as combines begin rolling.
"The question now is whether these rain events will continue during harvest," Snodgrass said, pointing to forecast models that suggest additional moisture could move into portions of the Midwest over the next one to two weeks.
While some areas of the Mid-South benefited from rapid crop dry-down and early harvest progress following prolonged drought conditions, other regions remain saturated. That includes portions of the Upper Midwest and areas extending into western Canada where soil moisture levels remain elevated.
Canadian Prairies Also in the Spotlight
The evolving pattern is not limited to the United States.
Forecast projections indicate that storm systems moving through western Canada could help maintain moisture across parts of the Prairies. While widespread harvest-disrupting rainfall is not guaranteed, Snodgrass said the developing flow pattern bears close monitoring because it may support recurring precipitation events rather than extended periods of dry weather.
A key feature is the emergence of a southwest-to-northeast storm track. As subtropical moisture interacts with northern weather systems, conditions may become more favourable for periodic rainfall across portions of the northern Plains and southern Prairie regions.
For Prairie growers harvesting cereals, canola and pulse crops, the timing and frequency of these systems could become important determinants of field access and crop quality.
Cooler Air Gives Way to Seasonal Swings
The first major taste of autumn has already arrived in parts of the northern United States.
Frost advisories have been issued in some northern production regions, while temperatures across portions of the Midwest recently dropped well below levels seen in the southern U.S.
However, Snodgrass does not expect cool conditions to dominate indefinitely.
Forecast models suggest temperatures will fluctuate through the remainder of September, with periodic warm-ups interrupting cooler periods. The exact temperature outlook remains uncertain because leading forecast models disagree on how long cool air will linger across the Midwest and Northeast.
For farmers, the combination of variable temperatures and periodic rainfall may create a more challenging harvest environment than the rapid dry-down conditions seen in some regions earlier this season.
Gulf Moisture Could Play a Larger Role
One element drawing increasing attention is the potential for moisture transport from the Gulf of Mexico.
Although the Atlantic hurricane season remains unusually quiet, Snodgrass said forecast guidance increasingly hints at stronger Gulf moisture connections developing later in September and into October.
Several artificial intelligence-enhanced weather models are indicating a broader zone of wetter conditions extending from the southern United States into portions of the central and northern Plains during the late September to early October period.
While confidence in specific storm tracks remains limited, the broader signal supports the possibility of renewed precipitation across agricultural regions that are entering peak harvest activity.
For grain producers, this could influence harvest timing, grain drying costs and transportation logistics if fields remain wetter than normal.
Strong El Niño Emerges as Major Winter Driver
Looking beyond harvest, Snodgrass believes one climate factor is becoming increasingly dominant: El Niño.
Ocean temperature measurements in the equatorial Pacific continue to strengthen, and current readings suggest the event could rank among the strongest on record. Forecast guidance indicates El Niño conditions are likely to persist through winter and potentially into next spring.
Historically, strong El Niño events have been associated with significant shifts in North American temperature and precipitation patterns, although outcomes can vary by region and month.
For producers in both the United States and Canada, the development raises important questions about winter conditions, spring moisture reserves and the outlook for the 2027 growing season.
Early projections indicate the atmosphere may increasingly favour a split jet stream pattern across North America, helping transport moisture across portions of the continent while also creating greater variability in temperature.
What Farmers Should Watch
As harvest accelerates, weather will remain a central focus for producers across the Midwest and Canadian Prairies.
Key factors to monitor include:
- Additional rainfall opportunities across the Midwest and northern Plains.
- Soil moisture levels in already saturated regions.
- The evolution of Gulf moisture transport into October.
- Temperature swings that could affect harvest pace.
- The continuing development of a historically strong El Niño event.
While significant uncertainty remains in longer-range forecasts, the overall message from current weather models is becoming clearer: the dry, ridge-dominated pattern of late summer is fading, and a wetter, more active autumn weather regime may be taking its place across major North American agricultural regions.
For farmers balancing harvest progress with crop quality concerns, that shift could become one of the defining stories of the season.
Watch the Nutrien Ag Solutions meteorologist Eric Snodgrass' predictions below.
Photo Credit: CARTO