Illinois, Iowa, Indiana, and Michigan Face Increasing Risk of Sustained Cold as EPS Weekly Signals Late-January Pattern Shift
ILLINOIS — New long-range ensemble data is signaling a meaningful turn toward colder-than-normal conditions across the Midwest, with Illinois positioned near the center of the strongest temperature anomaly expected to develop during the second half of January.
According to the latest ECMWF EPS weekly guidance, the Midwest and Great Lakes stand out as the most consistently cold region in the United States as atmospheric blocking increases at higher latitudes, allowing Arctic air to push south and linger.
Illinois and the Core Midwest Show the Strongest Cold Signal
Among all regions shown in the EPS temperature anomaly maps, Illinois, Iowa, Indiana, and southern Michigan fall within the most pronounced below-average temperature zone.
The ensemble mean indicates temperatures running several degrees below normal for an extended period, rather than brief cold shots. This places the Midwest at the highest confidence level for sustained cold compared to other parts of the country.
For Illinois specifically, the data suggests:
- Increased frequency of below-freezing daytime highs
- Longer overnight freezes
- A colder background pattern supportive of winter weather development
Great Lakes Region Also Impacted by Persistent Cold
The cold anomaly expands northeastward into Michigan, northern Indiana, and Ohio, placing much of the Great Lakes region under prolonged below-normal temperatures.
With colder air locked in place, the pattern raises the likelihood of:
- Lake-effect snow episodes
- Reduced melting between systems
- Accumulating snow persisting longer once it falls
This setup favors winter staying winter, especially as January moves toward its final weeks.
Secondary Cold Extends Into the Central Plains and Ohio Valley
Beyond the core Midwest, Missouri, Kentucky, and parts of the Ohio Valley also fall within the colder-than-average envelope, though anomalies there appear slightly weaker than over Illinois and the upper Midwest.
Still, these regions are expected to experience:
- More frequent cold intrusions
- Higher heating demand
- Increased chances of wintry precipitation during passing systems
Why Confidence Is Increasing
The key driver behind this forecast is high-latitude blocking, clearly visible in the geopotential height anomaly data. This type of pattern slows the jet stream and allows cold air to remain entrenched, rather than quickly retreating north.
When blocking appears consistently across multiple ensemble runs — as it does here — confidence increases that the colder trend will materialize.
Timing: When the Cold Becomes Established
The strongest signal aligns with late January, particularly the final 10–14 days of the month. While exact daily temperatures will fluctuate, the overall pattern favors cold dominance, especially across Illinois and neighboring states.
What to Watch Next
As January approaches, forecasters will monitor:
- Whether snow opportunities increase within the cold pattern
- How long blocking remains in place
- If the cold expands farther east or deepens over the Midwest
For now, the data is clear: Illinois and the Midwest are the primary targets of this developing colder regime.
Stay tuned to ChicagoMusicGuide.com for continued weather updates and Midwest-focused outlooks as winter conditions evolve.