🍂 Dr. Nick’s First Warn Fall Forecast 2025

Serving St. Louis • Southeast Missouri • Southern Illinois • Central Missouri

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Introduction: How We Built This Forecast

Fall in the Mid-Mississippi Valley is a moving target. Summer heat backs off, the jet stream sharpens, and small nudges in the Pacific can ripple all the way to St. Louis, Southeast Missouri, Southern Illinois, and Central Missouri. To make a sensible forecast for September through November, I use three pillars:

Climatology gives us the “normal” to measure against. September steadily cools, October brings the first frosts, and November delivers bigger fronts and the first flirt with winter. Everything else is a departure from this baseline.

Analog Years are past years that looked similar to our current setup. No two years are identical, but they can rhyme. When several past years share this year’s signals, they help shape expectations for temperature swings, storm timing, and frost risk.

Current Large-Scale Pattern factors like ocean temperatures, soil moisture, and the late-summer jet stream provide the steering currents that allow me to pick the right analogs and weight them correctly.

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What are “Analog Years”?

Analog years are past seasons that line up with today’s large-scale background. For 2025, the closest matches are 1998, 2005, 2010, and 2016.

These years shared:

• Neutral-to-weak La Niña setup in fall

• Negative PDO states

• Late-summer dryness in Missouri/Illinois

Analog outcomes for our region:

• September: Slightly warm overall, cool snaps late.

• October: Quieter early, wetter and stormier late.

• November: Sharp swings, first freezes, one or two soaking storms, flurries north.

These analog years give us confidence that the season will lean toward classic Midwest volatility. It’s worth noting that years like 2010 and 2016 both featured late-season storm systems that disrupted travel around Thanksgiving, while 2005 produced a surprisingly warm October before flipping to chilly, stormy conditions in November.

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La Niña Primer

La Niña is a cooling of tropical Pacific waters that tugs on the jet stream.

• September–October: More northwest flow → warm/cool flips.

• November: Stronger jet → deeper storm systems, windy rains, first flurries north.

• Severe Weather: Reduced overall, but late-October and November fronts still need watching.

In the Midwest, La Niña doesn’t always dominate fall in the way it dominates winter. Instead, its influence is subtle: cooler Pacific waters tend to tug the storm track north and west early, before letting deeper troughs dig south later in the season. This often translates to quieter early autumns and stormier Novembers.

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Other Contributing Factors

• PDO (Pacific Decadal Oscillation): Strongly negative → favors alternating mild/cool spells.

• Soil Moisture: Southern MO dry → warmer/drier early, less important once big October systems arrive.

• MJO: Tropical pulses could “flip” a 1–2 week wet/cool stretch.

• QBO: More winter player, less influence in fall.

Together, these large-scale factors tilt the scales toward a season that begins warmer and drier than average in September, then grows more active and variable as October and November progress.

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September 2025 – “Lingering Warmth, False Fall Snapshots”

Climatology

• Highs: 85°F → 76°F

• Lows: 66°F → 55°F

• Normal rainfall: ~3.1”

Forecast

• Temperatures: Near to slightly above normal. Upper 70s/low 80s common, with refreshing cool snaps late.

• Precipitation: Near to slightly below normal, especially SE MO.

• Storms: Sept 14–17, Sept 25–28 are frontal rain chances. Severe risk low but not zero.

• Snow: None.

• Frost: Highly unlikely except extreme north valleys.

• Nature’s Signs: Goldenrod blooms, ragweed peaks, early color on dogwoods, geese test flights.

Forecast Discussion

September will feel like two different months. The first half keeps the summer hangover alive — warm days, limited moisture, and dry frontal passages. The back half taps more Canadian air, delivering crisp mornings and windows-open weather. Dry soils in southern Missouri may exaggerate the warmth, but the message is: enjoy this stretch — harvest and outdoor events should go smoothly.

Analog years suggest that September will not feature much in the way of organized severe weather, but there can still be “sleeper” systems. In 2010, a mid-September front produced strong winds and a few hail reports across Missouri despite modest instability. This year’s setup echoes that — not a widespread severe risk, but enough instability and shear during mid-month to keep an eye on.

Atmospheric Setup: In September, the jet stream remains displaced north, often across the Dakotas into the Great Lakes. This keeps the storm track away from Missouri for the first half of the month. By the last 10 days, stronger Canadian highs press southward, pulling the jet with them and sharpening frontal boundaries. With Gulf moisture still sluggish, storms remain weak, but the stage is being set for the volatility to come.

Nature’s Signs Expanded: Goldenrod blooming in fields signals late-summer warmth giving way to shorter days. Ragweed peaks, triggering allergies, right before the first stronger fronts clear the air. Dogwoods turn early red in cool valleys, and geese start staging flights along the Mississippi flyway. These changes mirror the atmosphere’s transition — a subtle but steady reminder the season is shifting gears.

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October 2025 – “Crisp Nights, Color on the Hills”

Climatology

• Highs: 75°F → 64°F

• Lows: 55°F → 42°F

• Normal rainfall: ~3.4”

Forecast

• Temperatures: Near/slightly below normal. Highs mostly 60s/70s, raw 50s late.

• Precipitation: Near normal overall; drier early, wetter late.

• Storms: Oct 22–27, Oct 29–31 — main severe windows.

• Snow: Very low, but stray flurry north of I-70 possible late.

• Frost: Rural valleys Oct 15–25, Metro STL Oct 25–Nov 5.

• Nature’s Signs: Peak color mid-to-late month, deer rut begins, cricket chirps fade.

Forecast Discussion

October opens quietly, favoring cool, dry mornings and mild afternoons. But the jet strengthens by mid-month, and analogs point to late October as the “busy season.” If Gulf moisture returns, lines of storms could bring damaging winds. Otherwise, soaking rains will refresh soil moisture. Expect the first widespread frost outside of cities by the third week, with St. Louis proper running a week later.

Looking back at 1998 and 2016, both featured mild starts to October followed by dramatic shifts later in the month. In 2016, for example, temperatures near 80°F early in the month gave way to widespread frost and several rounds of strong storms after the 20th. That same pattern is possible this year, with the late-October windows standing out as the most likely for severe weather.

Atmospheric Setup: By October, the polar jet begins dipping farther south, and shortwaves ride the northwest flow into the Plains and Midwest. The Gulf of Mexico gradually “reopens” — a key ingredient for late-month storm chances. Canadian high pressure dominates early, but by the 20th, a more active storm track places Missouri and Illinois back into the path of systems that can tap both cool Canadian air and Gulf moisture.

Nature’s Signs Expanded: As nights cool, chlorophyll breaks down in leaves, revealing brilliant reds and oranges across Missouri’s hills. The deer rut begins under crisp mornings, often timed with the season’s first hard frosts in rural valleys. Crickets and katydids go silent, replaced by the crunch of fallen leaves. The natural world aligns with the atmosphere: quieter early, then more turbulent as stronger fronts sweep in.

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November 2025 – “First Freeze, Blustery Storms”

Climatology

• Highs: 59°F → 48°F

• Lows: 41°F → 32°F

• Normal rainfall: ~3.6”

Forecast

• Temperatures: Near normal, but variable: 60s one day, 30s the next.

• Precipitation: Near/slightly above normal. At least two soaking systems.

• Storms: Nov 8–11, Nov 18–21, Nov 24–28 (Thanksgiving week).

• Snow: First flurries possible north by Nov 18–27. STL Metro 10–20% chance of a trace.

• Freeze: Rural areas Nov 5–15; Metro STL Nov 15–25.

• Nature’s Signs: Oaks drop, gardens dormant, snow geese and ducks peak migration.

Forecast Discussion

November is the pivot into winter. Expect sharp swings: a 65° Sunday followed by a 38° Monday. At least one windy, soaking storm is likely in the first half of the month, and Thanksgiving week could feature a disruptive system. The analog set favors a clipper or southern stream system near Nov 24–28, bringing rain to most, but flurries to central/northern Missouri. First hard freeze hits rural areas early to mid-month, metro later.

Analog years back up this variability. In 2005, St. Louis saw highs in the 70s in early November before a Thanksgiving week cold front delivered rain, gusty winds, and the first flakes just north of the metro. 2010 featured a similar late-month storm, underscoring the pattern’s tendency to save its biggest punches for the holiday travel window.

Atmospheric Setup: By November, the subtropical jet strengthens, the polar jet deepens south, and troughs dig into the central U.S. This pattern brings more frequent frontal passages, often every 3–5 days. With soil moisture recharged, each system has more fuel for soaking rains. Cold Canadian highs build in stronger, producing hard freezes across the region. Storms track along the Ohio Valley, clipping Missouri and Illinois with wind, rain, and occasional flurries north of I-70.

Nature’s Signs Expanded: Oaks are among the last to drop leaves, signaling the true close of autumn. Gardens go dormant under frequent frosts. Flocks of snow geese and ducks fill the skies in peak migration, their movements cued by shortening days and the season’s first true cold surges. These natural milestones align with the atmosphere’s transition — the land, water, and sky all preparing for winter’s grip.

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Closing Thoughts

Fall 2025 is shaping up to be what I call a “classic Midwestern fall.” That means you’ll get everything: stretches of mild, beautiful days, the crunch of leaves underfoot, blustery November rains, and maybe even a few surprise flurries north of I-70 before December.

For farmers, September favors harvest progress, while October’s late rains may slow things briefly. For families, football and festivals get plenty of crisp air, but keep a backup plan for the last two weekends of October. For travelers, plan ahead — Thanksgiving week is a notorious storm window in these analog years.

More broadly, this fall continues a trend seen in past weak La Niña years where variability is the rule. Warmth can still sneak in, but sharp cold snaps and strong systems will remind us how quickly the season shifts. Communities should use the quiet early fall to prepare for a more active late stretch.

And finally, remember that fall often sets the stage for winter. If the analogs hold true, the late-season storminess of November may hint at an active early winter pattern. For now, though, enjoy the mix of crisp mornings, colorful foliage, and the occasional windy storm that makes fall in the Midwest unforgettable.

Stay safe, stay prepared, and enjoy the season.

— Dr. Nick