Forecasters are highly confident that an El Niño winter is on the horizon, and this could bring significant changes to weather conditions across the United States, including the Midwest. The National Weather Service’s Climate Prediction Center states that there is a greater than 95% chance of an El Niño continuing through the Northern Hemisphere winter, with a 71% chance of it being a strong El Niño. There is even a 30% chance that this El Niño could rival some of the strongest ones since 1950. However, forecasters caution that each El Niño event is unique, and a strong El Niño does not necessarily equate to strong local impacts.
El Niño refers to a period when sea-surface temperatures in the Pacific Ocean, particularly near the equator, are unusually warm. This leads to changes in weather patterns across the globe. During normal conditions, trade winds blow warm water from South America towards Asia, but during an El Niño, the trade winds weaken and warm water is pushed back east.
Typically, during an El Niño year, parts of the northern US and Canada experience drier and warmer conditions, while the Gulf Coast and Southeast see wetter-than-normal conditions and an increased risk of flooding. For Illinois, the impact of an El Niño event can vary depending on its size, intensity, and duration. Generally, summers tend to be slightly cooler and wetter, falls tend to be wetter and cooler, winters tend to be warmer and drier, springs tend to be drier, snowfall tends to be below average, and heating degree days tend to be below average, resulting in lower heating bills. The latest projections for the coming winter in the Chicago area suggest warmer-than-normal temperatures and below-normal precipitation. These projections align with how El Niño events typically unfold in Illinois and the Midwest.