5th Warmest November, 2nd Warmest Fall in Illinois

Temperature

This was the 5th warmest November on record for Illinois, based on preliminary data. The statewide average temperature was 47.4 degrees, and 4.9 degrees above normal. Here are the top ten warmest Novembers in Illinois since 1895:

  1. 2001 with 49.9°F
  2. 1931 with 49.1°F
  3. 1909 with 48.8°F
  4. 1999 with 48.4°F
  5. 2016 with 47.4°F 
  6. 2009 with 47.2°F
  7. 1902 with 46.9°F
  8. 1990 with 46.8°F
  9. 2015 with 46.6°F
  10. 1913 with 46.4°F

It was also the 2nd warmest fall on record for Illinois. The statewide average temperature for fall was 59.4 degrees, 5 degrees above normal. Only the fall of 1931 was warmer at 59.8 degrees. The climatological fall months are September, October, and November.

Precipitation

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Fall and Winter Forecast for Illinois

Summary: The NWS Climate Prediction Center has issued their forecasts for September, September-November (Fall), and December-February (Winter). Illinois has an increased chance of being warmer than normal this fall, and wetter than normal this winter.

According to the Climate Prediction Center, the main factors in the forecast are the recent warming trends and the expected La Niña. While the conditions in the Pacific are in the neutral stage between El Niño and La Niña, there is a 55-60 percent chance of a weak La Niña during fall and winter.

Fall

The September forecast (top row) has Illinois and the Midwest with equal chances of being above, below, and near-normal on both temperature and precipitation. I call this a neutral forecast since there are no indications that we will be significantly cooler, warmer, wetter, or drier.

The September-November forecast (bottom row) has Illinois and the US with an increased chance of being warmer than normal. They are neutral on the precipitation forecast.

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Winter

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Fifth Warmest Fall in Illinois

The average temperature for fall in Illinois (September-November) was 57.4 degrees, 3.0 degrees above average. As a result, it is the 5th warmest fall since 1895, based on preliminary data.

The top five warmest falls in Illinois:

  1. 1931 with 59.8 degrees
  2. 1963 with 58.0 degrees
  3. 1998 with 57.7 degrees
  4. 1971 with 57.5 degrees
  5. 2015 with 57.4 degrees

Here are the monthly departures of temperature in Illinois through the end of November for 2015. All three fall months were warmer than average. September was 4.6 degrees above average, October was 1.7 degrees above average, and November was 4.5 degrees above average.

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Monthly precipitation for 2015 shows the near-average September, the dry October, and the wet November. The 3-month total was 10.44 inches, 0.5 inches above average. Of course, this was overshadowed by the wet spring, especially June. In face, Illinois has already reached 41.79 inches of precipitation in 2015, 1.35 inches above the 12-month average.

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First Freeze of Season Hits Illinois

Over the weekend, most areas of the state saw their first taste of 32 degrees or colder. Here are the maps from the Midwestern Regional Climate Center showing that the almost the entire state was covered. A few places in the Chicago area may have escaped thanks to the so-called Urban Heat Island (UHI) – lots of warm surfaces like roads, asphalt parking lots, roofs, and waste heat from buildings. For example, O’Hare AP reached 33 degrees. Meanwhile, Mt. Carroll in northwest Illinois reported 20 degrees on October 18. Now that’s cold.

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Forecast for October, Fall, and Winter – Warmer Than Average

The NWS Climate Prediction Center released their latest outlook for October and beyond. It looks like the warm-than-average weather is expected to continue for the next several months. The primary driver in the forecast is the ongoing El Niño in the Pacific Ocean basin.

October

Illinois has an increased chance of above-average temperatures for October. There is not much to report on precipitation in Illinois. We are between drier-than-average conditions to our northeast and wetter-than-average conditions to our southwest.

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October-December

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Another Forecast Suggests a Higher Chance of a Wet Fall in Illinois

Last week, the NWS Climate Prediction Center released their official forecast for fall and winter. Their forecasters used a variety of tools and as well their own expertise to develop those forecasts. While their forecast for Illinois this winter was interesting, the one for fall was not.  They had us with equal chances of above-, below-, and near-average temperature and precipitation.

However, there is one forecast tool that showed some results for Illinois this fall. That tool is called the North American Multi-Model Ensemble (NMME). It consist of several forecast models that are run out to 7 months. The advantages of having multiple model runs are that an average of all results tends to be a better forecast than a single model. Also, the spread in the model results gives you an idea of the uncertainty of the forecast. For example, if all the models showed this winter being warmer-than-average, our confidence in the forecast would be much how than if some models showed it being warmer, some models showing colder, and others showing average conditions.

These results below for fall (SON=September, October, November) are considered experimental and not part of the NWS official forecast. However, they do shed some insight on what the models are “thinking” for fall. The first map show the chances on fall precipitation in three categories (wet, dry, average) using all models. They have Illinois and much of the US with an increased chance of above-average precipitation.

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Latest Seasonal Forecasts for Illinois – A Mild Winter?

The NWS Climate Prediction Center released their latest seasonal forecasts today. Here are the results for Illinois. The biggest news is that Illinois has an increased chance of above-average temperatures and below-average precipitation for the winter months of December, January, and February. This forecast is based largely on the developing El Niño in the Pacific Ocean.

While the forecast of a milder winter may sound appealing, I would not leave the winter coat in the closet and throw away the snow shovel just yet. Two things to consider are: 1) this is not a 100% guarantee, other factors come into play in determining our winter weather, and 2) even a mild winter can contain short periods of intense cold and abundant snowfall.

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More on the seasonal forecast

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