Revisiting the Chicago Halloween Snowstorm of 2019

While many kids were dressing up in costumes excited for Halloween festivities, Mother Nature also wore a disguise in 2019. Instead of fall attire, she wore a winter costume in the Midwest, with more tricks than treats for folks in northern Illinois. From October 29 - 31st, 2019, a complex series of weather systems traversed Canada and the United States, which set the stage for the unusual Chicagoland snowfall event.

Two days before the storm, a strong area of high presure set up over the Pacific and "ridged" the jet stream well north into Canada. This allowed deep, cold air from the Arctic to dive into the mid-section of the United States as the jet buckled south. This cold air moderated some as it moved along, but it remained cold enough for a rainy wave of low pressure to flip to mainly snow for northern Illinois late on the 30th and into the night. In fact, there was even a bit of sleet that mixed in overnight into the early morning on the 31st.

Although the first round of the system already dropped an inch or two of snow, the main slug of snow held off until the daytime on Halloween for Chicago and much of northern Illinois. In fact, many places reported moderate to heavy snow from the late morning into the afternoon hours of the 31st. As for amounts, many received 3 - 6" of snow, with the lowest amounts of 2 - 3" south of Chicago. The highest amounts topped out around 7 inches near Woodstock, IL, which is quite impressive for such an early storm. Chicago O'Hare recorded around 3.4" on the 31st, breaking the daily record of 0.1". The two-day total of 4.6" made October 2019 the second snowiest October on record, with the 6.3" inches in 1989 still holding on to the number one spot. The full extent of the Arctic airmass came in just behind the storm with gusty winds as well. Unseasonably cold temperatures ranging from the middle to upper 20s, combined with wind gusts as high as 30 - 35 mph, led to wind chills as low as the middle teens for some locations north and west of the city! This bitter airmass also brought the first hard-freeze in 2019, which typically holds off until November 3rd.

Despite the unusual timing and nature of this early-season snowstorm, WeatherWorks meteorologists began talking about the possibility of snow across the region as early as six days ahead of time, an impressive feat for any storm. Even with the extended lead time, the heavy snow brought widespread school closures and even delayed Halloween fesitivites for some towns. Additionally, the combination of the snow and gusty winds caused significant issues at O'Hare airport, with around 1,100 flights delayed during a 24-hour period. Similar issues were felt throughout the region, with around a hundred flights delayed at Midway airport. 

Blog lead photo of snow on autumn trees courtesy: 

Photo by Andre Benz on Unsplash