Will El Niño bring a snowy winter to Illinois and St. Louis? What forecasters expect

With unseasonably warm weather this week, metro-east residents may be wondering when it’s going to cool down. The first day of winter isn’t until Dec. 21, but the St. Louis region should see colder autumn weather before then.

“We’re going to get a true taste of fall this weekend, it’s going to be quite cool,” National Weather Service St. Louis meteorologist Alex Elmore told the News-Democrat Monday.

In fact, temperatures are forecast to be below normal this weekend, with lows reaching the 40s Saturday. The upcoming drop in temperatures can be attributed to a series of cold fronts, though some weather patterns last much longer than these typical dips.

For the first time in several years, an El Niño weather pattern is emerging. The terms El Niño and La Niña refer to climate patterns determined by tradewinds and water temperatures.

We see El Niño occur when tradewinds are weakened and warm water is pushed east, the National Oceanic and Atmospheric Administration reports. We are gradually moving into an El Niño pattern after a period of La Niña, Elmore said.

“The pattern this upcoming winter is going to be dominated by El Niño,” Elmore said, but the season’s weather will also be affected by smaller patterns and determining factors.

The Midwest generally sees a little bit warmer and drier weather during El Niño, Elmore continued, but since the pattern could last multiple years, it doesn’t necessarily mean this entire winter will be warm or dry. It simply means the region will see warmer and drier weather than typical more often than not in this El Niño stretch.

The weather service’s three-month seasonal outlook predicts residents of the St. Louis region have roughly equal chances of experiencing above- or below-normal temperatures and precipitation this October through December.

It’s a little early to provide a general forecast for this winter, Elmore said, and NWS forecasters expect to have a better idea closer to late October or mid-November.

Here’s what to know about typical winter weather in southwestern Illinois and St. Louis, as well as a prediction from the Farmers’ Almanac.

Typical winter weather in Belleville

The NWS St. Louis office provides monthly climate data from 1991 to 2020. Here’s what to know about average weather from October to February in Belleville.

October:

  • Average minimum temperature: 46.7 degrees Fahrenheit

  • Average maximum temperature: 72.6 degrees

  • Average overall temperature: 59.7 degrees

  • Total normal precipitation: 3.12 inches

November:

  • Average minimum temperature: 36.9 degrees

  • Average maximum temperature: 58.1 degrees

  • Average overall temperature: 47.5 degrees

  • Total normal precipitation: 3.6 inches

December:

  • Average minimum temperature: 28.3 degrees

  • Average maximum temperature: 46.3 degrees

  • Average overall temperature: 37.3 degrees

  • Total normal precipitation: 2.61 inches

January:

  • Average minimum temperature: 24.3 degrees

  • Average maximum temperature: 42.9 degrees

  • Average overall temperature: 33.6 degrees

  • Total normal precipitation: 2.56 inches

February:

  • Average minimum temperature: 28 degrees

  • Average maximum temperature: 48.6 degrees

  • Average overall temperature: 38.3 degrees

  • Total normal precipitation: 2.16 inches

The St. Louis area generally sees the season’s first frost around Oct. 21, Elmore said.

The average temperature in St. Clair County last October was 55.8 degrees, according to data from the National Centers for Environmental Information. Here’s more on average temperatures in St. Clair County:

Note: This graphic will automatically update as new data becomes available.

Farmers’ Almanac winter predictions

The Farmers’ Almanac’s 2023 to 2024 Extended Weather Forecast predicts traditional cool temperatures and snowy weather conditions across the U.S.

The almanac expects Illinois will see a “cold, stormy” season, while Missouri residents will experience “cold” temperatures with “average snowfall.”

The organization makes predictions based on a mysterious formula that considers factors such as planetary positioning, sunspot activity and tidal action of the moon.

“The only person who knows the exact formula is the Farmers’ Almanac weather prognosticator who goes by the pseudonym of Caleb Weatherbee,” the organization’s website says. “To protect this proprietary formula, the editors of the Farmers’ Almanac prefer to keep both Caleb’s true identity and the formula a closely guarded brand secret.”

The almanac has provided extended forecasts since 1818, according to its website.