Chicago Weather Forecast: Sudden Arctic Blast and Heavy Snow Arrive—See Hour-By-Hour Outlook

Morning Fog Blankets the City A Dense Fog Advisory remains in effect for Cook and Lake counties through 6 a.m. Friday, slashing visibility to a quarter-mile or less and complicating the early commute. Drivers should use low-beam headlights and allow extra stopping distance while traveling across Chicago’s lakefront, interstates, and suburban corridors. Two Rounds of Storms on Tap Forecasters expect two distinct waves of thunderstorms today. • Round 1: Showers and isolated rumbles arrive before sunrise, riding north from central Illinois. • Round 2: A stronger line develops along a fast-moving cold front late this afternoon, between 3 p.m. and 8 p.m., bringing the main severe threat. Primary hazards include torrential rain, frequent lightning, and wind gusts topping 50 mph, which could down tree limbs and cause scattered outages. While the tornado risk is low, an isolated spin-up can’t be ruled out south of I-80 as the front sweeps through rapidly warming air. Near-Record Warmth Ahead of the Front Before storms fire, southerly winds will pump unseasonably warm air into the metro. Thermometers are projected to surge to 68–71 °F—close to the March 6 record of 72 °F set in 2000—making the day feel more like late April than early March. Humidity will climb as well, adding a sticky edge to the spring preview. Evening Temperature Plunge Once the front passes, temperatures tumble into the upper 40s by midnight and hold in the 40s Saturday, accompanied by brisk northwest winds and lingering spotty showers. Sunday turns cooler still, with highs near 42 °F under partly sunny skies, before a gradual warm-up returns early next week. What Chicagoans Should Do Now • Plan for extra drive time this morning; transit riders should check for possible delays. • Secure loose outdoor items before storms arrive. • Have multiple ways to receive weather warnings—NOAA radio, mobile alerts, or local TV. • If thunder roars, head indoors; the safest place during a storm is a sturdy building, not under a tree or on a porch. • After the front, dress in layers—temperatures will drop more than 20 degrees in just a few hours. Bottom Line Today’s Chicago weather forecast features a one-two punch: dense fog to start, followed by potent afternoon thunderstorms and a sharp cold-front cooldown. Staying weather-aware will help you navigate the fog, ride out the storms, and prepare for a cooler weekend ahead.