Dense Fog Advisories in Illinois, 2021

Dense Fog Advisories by county

Each county as a circle sized by its count in 2021. Tap one for its archive.

Over time

By month

The alerts

Every alert, in the order issued. Times are local, Central Time. Each opens its own page with the text, the map, the radar and the sounding.

Issued	Product	Office	Counties	Lasted
Jan 2, 2:33 PM CST	Dense Fog Advisory	LSX	Adams, Brown, Pike	21 hr
Jan 2, 2:49 PM CST	Dense Fog Advisory	DVN	Bureau, Carroll, Hancock, Henderson, Henry, Jo Daviess and 7 more	21 hr
Jan 2, 3:04 PM CST	Dense Fog Advisory	LOT	Boone, DeKalb, Grundy, Kane, Kendall, LaSalle and 5 more	20 hr
Jan 2, 3:49 PM CST	Dense Fog Advisory	ILX	Cass, Fulton, Knox, Logan, McLean, Marshall and 10 more	18 hr
Jan 3, 1:55 PM CST	Dense Fog Advisory	LSX	Adams, Brown, Calhoun, Fayette, Greene, Jersey and 7 more	30 hr
Jan 3, 2:22 PM CST	Dense Fog Advisory	DVN	Bureau, Carroll, Hancock, Henderson, Henry, Jo Daviess and 7 more	28 hr
Jan 3, 2:38 PM CST	Dense Fog Advisory	ILX	Cass, Champaign, Christian, Clark, Coles, Cumberland and 24 more	32 hr
Jan 3, 3:37 PM CST	Dense Fog Advisory	LOT	Boone, Cook, DeKalb, DuPage, Ford, Grundy and 11 more	29 hr
Jan 4, 5:30 AM CST	Dense Fog Advisory	PAH	Jackson	5 hr
Jan 5, 3:18 PM CST	Dense Fog Advisory	LOT	Boone, DeKalb, DuPage, Ford, Grundy, Iroquois and 10 more	19 hr
Jan 5, 3:27 PM CST	Dense Fog Advisory	ILX	Cass, Champaign, Christian, Coles, DeWitt, Douglas and 21 more	17 hr
Jan 5, 3:41 PM CST	Dense Fog Advisory	DVN	Bureau, Carroll, Hancock, Henderson, Henry, Jo Daviess and 7 more	18 hr
Jan 5, 7:17 PM CST	Dense Fog Advisory	LSX	Adams, Brown, Fayette, Greene, Macoupin, Montgomery and 1 more	13 hr
Jan 6, 2:32 PM CST	Dense Fog Advisory	ILX	Fulton, Knox, Peoria, Stark	7 hr
Jan 6, 2:37 PM CST	Dense Fog Advisory	DVN	Carroll, Hancock, Henderson, Henry, Jo Daviess, McDonough and 5 more	13 hr
Jan 15, 10:33 PM CST	Dense Fog Advisory	LOT	Cook, Grundy, Kankakee, Kendall, Will	4 hr
Jan 25, 9:24 PM CST	Dense Fog Advisory	PAH	Alexander, Edwards, Franklin, Gallatin, Hamilton, Hardin and 13 more	12 hr
Feb 2, 2:51 PM CST	Dense Fog Advisory	LSX	Adams, Brown, Pike	20 hr
Feb 3, 1:04 AM CST	Dense Fog Advisory	DVN	Bureau, Carroll, Hancock, Henderson, Henry, Jo Daviess and 5 more	10 hr
Feb 3, 5:47 AM CST	Dense Fog Advisory	LOT	Boone, DeKalb, Grundy, Kankakee, LaSalle, Lee and 4 more	5 hr
Feb 26, 1:19 AM CST	Dense Fog Advisory	DVN	Jo Daviess	4 hr
Feb 27, 5:30 AM CST	Dense Fog Advisory	LOT	Cook, DeKalb, DuPage, Ford, Grundy, Iroquois and 6 more	6 hr
Feb 28, 6:13 AM CST	Dense Fog Advisory	DVN	Bureau, Carroll, Hancock, Henderson, Henry, Jo Daviess and 7 more	6 hr
Feb 28, 6:29 AM CST	Dense Fog Advisory	LOT	Boone, Cook, DeKalb, DuPage, Grundy, Kane and 9 more	6 hr
Feb 28, 6:57 AM CST	Dense Fog Advisory	ILX	Fulton, Knox, Marshall, Peoria, Schuyler, Stark	3 hr
Mar 16, 12:22 AM CDT	Dense Fog Advisory	ILX	Cass, Champaign, Christian, Clark, Clay, Coles and 29 more	10 hr
Mar 16, 12:37 AM CDT	Dense Fog Advisory	DVN	Hancock, Henderson, McDonough, Mercer, Warren	9 hr
Mar 16, 12:58 AM CDT	Dense Fog Advisory	LSX	Adams, Bond, Brown, Calhoun, Clinton, Fayette and 11 more	9 hr
Mar 16, 1:22 AM CDT	Dense Fog Advisory	PAH	Edwards, Franklin, Gallatin, Hamilton, Jackson, Jefferson and 6 more	9 hr
Apr 25, 2:43 AM CDT	Dense Fog Advisory	PAH	Alexander, Edwards, Franklin, Gallatin, Hamilton, Hardin and 13 more	6 hr
May 24, 1:43 AM CDT	Dense Fog Advisory	LOT	Cook, Lake	4 hr
Jun 1, 1:18 AM CDT	Dense Fog Advisory	DVN	Bureau, Hancock, Henderson, Henry, McDonough, Mercer and 3 more	8 hr
Jun 1, 1:20 AM CDT	Dense Fog Advisory	ILX	Fulton, Knox, Marshall, Peoria, Stark	6 hr
Jun 10, 4:51 AM CDT	Dense Fog Advisory	ILX	Clark, Clay, Coles, Crawford, Cumberland, Effingham and 5 more	3 hr
Jun 11, 3:42 AM CDT	Dense Fog Advisory	ILX	Clark, Clay, Crawford, Cumberland, Effingham, Jasper and 2 more	4 hr
Jun 11, 6:16 AM CDT	Dense Fog Advisory	PAH	Edwards, Franklin, Gallatin, Hamilton, Hardin, Jefferson and 7 more	3 hr
Jul 1, 4:24 AM CDT	Dense Fog Advisory	DVN	Bureau, Hancock, Henderson, Henry, McDonough, Mercer and 3 more	4 hr
Jul 18, 7:11 AM CDT	Dense Fog Advisory	ILX	Champaign, Christian, Clark, Coles, Crawford, Cumberland and 10 more	3 hr
Aug 1, 1:03 AM CDT	Dense Fog Advisory	ILX	Cass, Christian, DeWitt, Fulton, Logan, McLean and 13 more	7 hr
Aug 1, 1:58 AM CDT	Dense Fog Advisory	LSX	Adams, Brown, Calhoun, Greene, Jersey, Macoupin and 2 more	6 hr
Aug 20, 5:23 AM CDT	Dense Fog Advisory	LOT	Cook, Lake, McHenry	3 hr
Aug 22, 2:45 AM CDT	Dense Fog Advisory	ILX	Clark, Clay, Coles, Crawford, Cumberland, Douglas and 6 more	6 hr
Aug 22, 3:43 AM CDT	Dense Fog Advisory	PAH	Edwards, Gallatin, Hamilton, Hardin, Wabash, Wayne and 1 more	4 hr
Aug 23, 3:51 AM CDT	Dense Fog Advisory	ILX	Champaign, Christian, Clark, Clay, Coles, Crawford and 15 more	4 hr
Sep 25, 5:02 AM CDT	Dense Fog Advisory	ILX	Cass, Christian, Morgan, Sangamon, Schuyler, Scott	4 hr
Sep 25, 5:06 AM CDT	Dense Fog Advisory	LSX	Adams, Brown, Calhoun, Greene, Jersey, Macoupin and 2 more	4 hr
Oct 6, 8:36 PM CDT	Dense Fog Advisory	LSX	Adams, Brown, Pike	12 hr
Oct 7, 8:38 PM CDT	Dense Fog Advisory	LSX	Adams, Bond, Brown, Calhoun, Clinton, Fayette and 9 more	12 hr
Oct 7, 8:41 PM CDT	Dense Fog Advisory	ILX	Cass, Champaign, Christian, Clark, Clay, Coles and 29 more	13 hr
Oct 8, 3:52 AM CDT	Dense Fog Advisory	DVN	Carroll, Jo Daviess, Stephenson	5 hr
Oct 8, 5:45 AM CDT	Dense Fog Advisory	PAH	Alexander, Edwards, Franklin, Gallatin, Hamilton, Hardin and 13 more	3 hr
Oct 8, 5:52 AM CDT	Dense Fog Advisory	LOT	Boone, Cook, DeKalb, DuPage, Kane, Kendall and 6 more	3 hr
Oct 8, 9:43 PM CDT	Dense Fog Advisory	DVN	Bureau, Carroll, Henry, Jo Daviess, Mercer, Putnam and 3 more	10 hr
Oct 8, 9:45 PM CDT	Dense Fog Advisory	ILX	Knox, McLean, Marshall, Peoria, Stark, Tazewell and 1 more	6 hr
Oct 8, 9:45 PM CDT	Dense Fog Advisory	LOT	Boone, Cook, DeKalb, DuPage, Ford, Grundy and 12 more	6 hr
Oct 13, 12:21 AM CDT	Dense Fog Advisory	LOT	Cook, DeKalb, DuPage, Kane, Kankakee, Kendall and 1 more	8 hr
Nov 10, 2:28 AM CST	Dense Fog Advisory	LOT	Ford, Iroquois, Kankakee	7 hr
Nov 10, 2:35 AM CST	Dense Fog Advisory	ILX	Champaign, Clark, Coles, Crawford, Cumberland, DeWitt and 10 more	6 hr
Dec 2, 2:00 AM CST	Dense Fog Advisory	PAH	Alexander, Edwards, Franklin, Gallatin, Hamilton, Hardin and 11 more	4 hr
Dec 3, 10:49 PM CST	Dense Fog Advisory	LOT	Boone, DeKalb, Kane, Lake, Lee, McHenry and 2 more	3 hr
Dec 4, 6:13 AM CST	Dense Fog Advisory	LOT	Ford, Grundy, Iroquois, Kankakee, Kendall, LaSalle and 2 more	3 hr
Dec 10, 12:19 AM CST	Dense Fog Advisory	ILX	Cass, Champaign, Christian, Clark, Clay, Coles and 23 more	11 hr
Dec 10, 12:27 AM CST	Dense Fog Advisory	LOT	Ford, Grundy, Iroquois, Kankakee, Livingston, Will	12 hr
Dec 10, 2:28 AM CST	Dense Fog Advisory	LSX	Bond, Calhoun, Clinton, Fayette, Greene, Jersey and 9 more	9 hr
Dec 25, 11:52 PM CST	Dense Fog Advisory	DVN	Bureau, Hancock, Henderson, Henry, McDonough, Putnam and 1 more	12 hr
Dec 25, 11:55 PM CST	Dense Fog Advisory	LSX	Adams, Bond, Brown, Calhoun, Clinton, Fayette and 11 more	12 hr
Dec 25, 11:55 PM CST	Dense Fog Advisory	PAH	Alexander, Franklin, Gallatin, Hamilton, Hardin, Jackson and 10 more	10 hr
Dec 26, 1:13 AM CST	Dense Fog Advisory	ILX	Cass, Christian, DeWitt, Fulton, Knox, Logan and 13 more	11 hr
Dec 27, 8:11 AM CST	Dense Fog Advisory	LOT	Boone, Cook, DeKalb, DuPage, Ford, Grundy and 9 more	4 hr
Dec 29, 7:31 AM CST	Dense Fog Advisory	PAH	Alexander, Gallatin, Hardin, Jackson, Johnson, Massac and 5 more	2 hr
Dec 29, 10:01 PM CST	Dense Fog Advisory	PAH	Alexander, Franklin, Gallatin, Hamilton, Hardin, Jackson and 11 more	11 hr
Dec 29, 10:09 PM CST	Dense Fog Advisory	LSX	Bond, Calhoun, Clinton, Fayette, Jersey, Madison and 5 more	14 hr
Dec 30, 7:17 PM CST	Dense Fog Advisory	DVN	Bureau, Carroll, Hancock, Henderson, Henry, Jo Daviess and 7 more	23 hr
Dec 30, 9:23 PM CST	Dense Fog Advisory	LSX	Adams, Bond, Brown, Calhoun, Clinton, Fayette and 8 more	15 hr
Dec 30, 9:28 PM CST	Dense Fog Advisory	ILX	Cass, Champaign, Christian, Clark, Clay, Coles and 29 more	13 hr

By county

Every county with at least one alert. A county page lists each alert that covered it.

62 more counties

The busiest days

Days with the most alerts issued, by UTC date.

Nearby

Alerts in force now Tornadoes on record The radar archive 2020 2022

Sources

National Weather Service watches, warnings, advisories and statements from the Iowa Environmental Mesonet's VTEC archive, which reconstructs tornado, severe thunderstorm, flash flood and marine warnings back to 1986 from the NWS text archive. Storm Prediction Center watches and mesoscale discussions from SPC's archive through the Mesonet. County centers from the US Census Bureau. Rebuilt daily.