The National Weather Service has issued a red flag warning in some Chicago-area counties Friday. The warning – in effect in DeKalb, Kane, LaSalle, Kendall, and Grundy counties – is set to remain in place through the evening hours, warning of significant fire risks. “Any fire that develops will catch and spread quickly. Outdoor burning is not recommended,” the warning from the National Weather Service states.
What is a red flag warning? According to the NWS, a red flag warning is issued when the combination of dry fuels and weather conditions supports extreme fire danger. For northern Illinois and northwest Indiana, the red flag warning criteria include sustained 20-foot winds of 20 mph or higher, relative humidity less than 25%, and 10-hour fuel moisture at 8% per day. “A red flag warning means that critical fire weather conditions are either occurring now or will shortly,” the NWS said in the alert issued Friday. “A combination of strong winds, relative humidity, and warm temperatures can contribute to extreme fire behavior.”
What is the difference between a red flag warning and a fire watch? According to NWS, the two alerts are similar. “A Fire Weather Watch is issued up to 72 hours before the above conditions are expected to occur,” the agency reported. “A Red Flag Warning is issued when the conditions above are expected to occur or are occurring within the next 24 hours.” The red flag warning will include the counties of DeKalb, Kane, LaSalle, Kendall, and Grundy. It was issued just after 9:30 a.m. and remains in effect until 7 p.m. “Today will be very warm with low relative humidity and strengthening winds, with gusts to 45 mph at times this afternoon,” the NWS warned. “This combination will lead to an increased threat for fire spread, particularly where little/no rain fell on Thursday.”
What should you do if you’re under a red flag warning? The NWS urges anyone under the warning to “avoid activities that cause open flames or sparks.” That includes activities like operating farm equipment, parking on grass, or discarding smoking materials. Outdoor burning is not recommended. Those on East-West roads are also being asked to use caution with high-profile vehicles. Strong wind gusts may continue through midnight, the agency warned. Additionally, today will be very warm with low relative humidity and strengthening winds, with gusts to 45 mph at times this afternoon. This combination will lead to an increased threat for fire spread, particularly where little/no rain fell on Thursday.
