Alert archive / Illinois / Grundy County
Weather alerts in Grundy County, Illinois, 2020
132 weather alerts in 2020, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Grundy County and its neighbors
Each county as a circle sized by its count in 2020. Tap one for its archive.
- Alerts
- 132
- Warnings
- 26
- Watches
- 21
- Advisories
- 50
- Busiest month
- May30 alerts
- Busiest day
- May 15, 202010 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
0 of 2 tornado reports fell inside a warning.
Grundy County, 2020
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 2 | 0% | |||
| Severe thunderstorm warnings | 7 | 4 | 43% | 9 | 89% | 39 min |
| Flash flood warnings | 2 | 2 | 0% | 0 |
Each office's whole area, 2020
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Chicago, IL: tornado warnings | 25 | 5 | 80% | 35 | 37% | 13 min |
| NWS Chicago, IL: severe thunderstorm warnings | 112 | 77 | 31% | 443 | 83% | 33 min |
| NWS Chicago, IL: flash flood warnings | 19 | 11 | 42% | 64 | 83% | 114 min |
An office's figures cover every county it serves, including across state lines.
Verified by the Iowa Environmental Mesonet's Cow, which matches each storm-based warning with the local storm reports inside its polygon while it was in force, within 15 km of its edge: a tornado warning counts as verified on a tornado report, a severe thunderstorm warning on hail of 1 inch or more, a gust of 58 mph or more, or wind damage, a flash flood warning on a flash flood report. The false alarm ratio is the share of warnings with no such report; "inside a warning" is the probability of detection, the share of reports that fell inside one; lead time runs from the warning's issue to each report inside it, counting zero for a report that came first. A warning with no report is not proof nothing happened: reports come from spotters, the public and damage surveys, and are thin where few people live.
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 | Lasted |
|---|---|---|---|
| Jan 9, 3:20 AM CST | Wind Advisory | LOT | 15 hr |
| Jan 9, 3:39 AM CST | Flood Watch | LOT | 55 hr |
| Jan 9, 10:58 AM CST | River Flood Warning | LOT | 70 hr |
| Jan 9, 11:15 AM CST | River Flood Watch | LOT | 4 days |
| Jan 9, 11:23 AM CST | River Flood Watch | LOT | 21 days |
| Jan 10, 10:54 AM CST | River Flood Warning | LOT | 57 hr |
| Jan 10, 11:44 AM CST | Winter Weather Advisory | LOT | 38 hr |
| Jan 11, 8:51 AM CST | River Flood Warning | LOT | 45 hr |
| Jan 11, 3:10 PM CST | Mesoscale Discussion | SPC | 4 hr |
| Jan 11, 8:24 PM CST | River Flood Advisory | LOT | 19 hr |
| Jan 12, 7:37 PM CST | Winter Weather Advisory | LOT | 7 hr |
| Jan 16, 2:44 PM CST | Winter Weather Advisory | LOT | 51 hr |
| Jan 18, 2:24 PM CST | Wind Chill Advisory | LOT | 20 hr |
| Jan 24, 3:12 AM CST | Winter Weather Advisory | LOT | 35 hr |
| Jan 24, 8:34 AM CST | Dense Fog Advisory | LOT | 11 hr |
| Feb 8, 1:38 PM CST | Winter Weather Advisory | LOT | 26 hr |
| Feb 11, 2:38 PM CST | Winter Weather Advisory | LOT | 52 hr |
| Feb 13, 2:07 PM CST | Wind Chill Advisory | LOT | 20 hr |
| Feb 17, 8:24 PM CST | Dense Fog Advisory | LOT | 6 hr |
| Feb 23, 2:11 PM CST | Winter Storm Watch | LOT | 48 hr |
| Feb 25, 3:34 AM CST | Winter Weather Advisory | LOT | 38 hr |
| Mar 5, 2:10 PM CST | Wind Advisory | LOT | 22 hr |
| Mar 25, 4:39 AM CDT | Dense Fog Advisory | LOT | 6 hr |
| Mar 28, 2:43 PM CDT | Wind Advisory | LOT | 29 hr |
| Mar 28, 8:06 PM CDT | Mesoscale Discussion | SPC | 54 min |
| Mar 28, 8:41 PM CDT | Tornado Watch | SPC | 3 hr |
| Mar 28, 10:23 PM CDT | Mesoscale Discussion | SPC | 97 min |
| Apr 6, 11:03 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Apr 7, 5:07 PM CDT | Mesoscale Discussion | SPC | 83 min |
| Apr 7, 7:22 PM CDT | Mesoscale Discussion | SPC | 83 min |
| Apr 8, 3:08 PM CDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Apr 9, 3:18 AM CDT | Wind Advisory | LOT | 16 hr |
| Apr 12, 3:57 AM CDT | Wind Advisory | LOT | 36 hr |
| Apr 15, 5:22 AM CDT | Winter Weather Advisory | LOT | 5 hr |
| Apr 16, 3:28 AM CDT | Winter Weather Advisory | LOT | 32 hr |
| Apr 26, 3:15 AM CDT | River Flood Advisory | LOT | 24 hr |
| Apr 28, 4:51 PM CDT | Mesoscale Discussion | SPC | 114 min |
| Apr 29, 10:47 AM CDT | River Flood Advisory | LOT | 20 hr |
| Apr 29, 11:21 AM CDT | River Flood Advisory | LOT | 10 hr |
| Apr 29, 8:48 PM CDT | Areal Flood Advisory | LOT | 7 hr |
| Apr 29, 9:33 PM CDT | River Flood Advisory | LOT | 9 hr |
| Apr 29, 9:40 PM CDT | River Flood Warning | LOT | 57 hr |
| Apr 30, 3:48 AM CDT | Areal Flood Advisory | LOT | 6 hr |
| Apr 30, 6:34 AM CDT | River Flood Warning | LOT | 14 hr |
| Apr 30, 6:41 AM CDT | River Flood Warning | LOT | 20 hr |
| May 7, 3:33 AM CDT | Freeze Watch | LOT | 24 hr |
| May 8, 3:56 AM CDT | Freeze Warning | LOT | 27 hr |
| May 11, 2:45 PM CDT | Frost Advisory | LOT | 17 hr |
| May 14, 11:26 AM CDT | River Flood Advisory | LOT | 25 hr |
| May 14, 12:06 PM CDT | Flash Flood Watch | LOT | 17 hr |
| May 14, 6:15 PM CDT | Severe Thunderstorm Watch | SPC | 8 hr |
| May 14, 8:32 PM CDT | Areal Flood Advisory | LOT | 4 hr |
| May 14, 9:14 PM CDT | Flash Flood Warning | LOT | 6 hr |
| May 15, 1:06 AM CDT | Mesoscale Discussion | SPC | 114 min |
| May 15, 1:35 AM CDT | Areal Flood Advisory | LOT | 115 min |
| May 15, 2:02 AM CDT | River Flood Advisory | LOT | 36 hr |
| May 15, 2:02 AM CDT | River Flood Advisory | LOT | 15 hr |
| May 15, 3:01 AM CDT | Areal Flood Warning | LOT | 6 hr |
| May 15, 11:58 AM CDT | River Flood Warning | LOT | 7 days |
| May 15, 4:45 PM CDT | River Flood Warning | LOT | 20 hr |
| May 15, 5:00 PM CDT | River Flood Warning | LOT | 4 days |
| May 16, 2:47 PM CDT | Flash Flood Watch | LOT | 32 hr |
| May 16, 8:00 PM CDT | River Flood Watch | LOT | 17 hr |
| May 17, 12:49 PM CDT | River Flood Warning | LOT | 7 days |
| May 17, 1:44 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| May 17, 2:14 PM CDT | Areal Flood Advisory | LOT | 3 hr |
| May 17, 3:29 PM CDT | Areal Flood Advisory | LOT | 94 min |
| May 17, 4:32 PM CDT | Flash Flood Warning | LOT | 6 hr |
| May 17, 10:10 PM CDT | Areal Flood Warning | LOT | 30 hr |
| May 18, 11:59 AM CDT | Mesoscale Discussion | SPC | 91 min |
| May 23, 12:33 PM CDT | Tornado Watch | SPC | 8 hr |
| May 23, 2:08 PM CDT | Severe Thunderstorm Warning | LOT | 67 min |
| May 23, 2:39 PM CDT | Severe Thunderstorm Warning | LOT | 51 min |
| May 23, 2:51 PM CDT | Mesoscale Discussion | SPC | 84 min |
| May 24, 8:57 AM CDT | River Flood Advisory | LOT | 25 hr |
| Jun 5, 12:26 PM CDT | Mesoscale Discussion | SPC | 94 min |
| Jun 9, 2:33 AM CDT | Wind Advisory | LOT | 21 hr |
| Jun 9, 6:20 PM CDT | Mesoscale Discussion | SPC | 115 min |
| Jun 22, 12:48 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 22, 1:36 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 22, 3:02 PM CDT | Special Weather Statement | LOT | 43 min |
| Jun 22, 3:38 PM CDT | Mesoscale Discussion | SPC | 97 min |
| Jun 22, 5:40 PM CDT | Special Weather Statement | LOT | 50 min |
| Jun 22, 6:53 PM CDT | Areal Flood Advisory | LOT | 3 hr |
| Jun 26, 1:38 PM CDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jun 26, 3:39 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 26, 8:04 PM CDT | Special Weather Statement | LOT | 56 min |
| Jun 26, 8:22 PM CDT | Severe Thunderstorm Warning | LOT | 53 min |
| Jun 26, 10:37 PM CDT | Areal Flood Advisory | LOT | 3 hr |
| Jul 9, 2:51 PM CDT | Mesoscale Discussion | SPC | 114 min |
| Jul 9, 5:39 PM CDT | Mesoscale Discussion | SPC | 96 min |
| Jul 11, 3:58 PM CDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jul 11, 7:17 PM CDT | Mesoscale Discussion | SPC | 58 min |
| Jul 11, 9:15 PM CDT | Severe Thunderstorm Warning | LOT | 60 min |
| Jul 15, 3:14 PM CDT | Tornado Watch | SPC | 6 hr |
| Jul 15, 5:35 PM CDT | Mesoscale Discussion | SPC | 85 min |
| Jul 17, 3:36 AM CDT | Heat Advisory | LOT | 40 hr |
| Jul 19, 5:28 AM CDT | Special Weather Statement | LOT | 62 min |
| Jul 19, 6:22 AM CDT | Special Weather Statement | LOT | 53 min |
| Jul 19, 8:16 AM CDT | Special Weather Statement | LOT | 44 min |
| Jul 19, 8:44 AM CDT | Areal Flood Advisory | LOT | 6 hr |
| Jul 19, 10:12 AM CDT | Mesoscale Discussion | SPC | 93 min |
| Jul 19, 10:32 AM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Jul 19, 10:35 AM CDT | Severe Thunderstorm Warning | LOT | 40 min |
| Aug 10, 10:42 AM CDT | Mesoscale Discussion | SPC | 93 min |
| Aug 10, 11:26 AM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Aug 10, 1:36 PM CDT | Mesoscale Discussion | SPC | 114 min |
| Aug 10, 2:24 PM CDT | Severe Thunderstorm Warning | LOT | 96 min |
| Aug 10, 3:36 PM CDT | Mesoscale Discussion | SPC | 84 min |
| Aug 10, 4:23 PM CDT | High Wind Warning | LOT | 90 min |
| Aug 15, 4:40 PM CDT | Mesoscale Discussion | SPC | 95 min |
| Oct 4, 3:46 AM CDT | Frost Advisory | LOT | 28 hr |
| Oct 14, 3:33 AM CDT | Wind Advisory | LOT | 15 hr |
| Oct 14, 3:44 AM CDT | Red Flag Warning | LOT | 15 hr |
| Oct 14, 7:41 PM CDT | Freeze Watch | LOT | 7 hr |
| Oct 15, 2:35 AM CDT | Freeze Warning | LOT | 30 hr |
| Oct 16, 2:40 PM CDT | Wind Advisory | LOT | 28 hr |
| Oct 16, 2:52 PM CDT | Fire Weather Watch | LOT | 12 hr |
| Oct 16, 2:52 PM CDT | Red Flag Warning | LOT | 29 hr |
| Oct 21, 10:48 PM CDT | Special Weather Statement | LOT | 42 min |
| Oct 22, 3:30 AM CDT | Dense Fog Advisory | LOT | 9 hr |
| Oct 31, 10:44 AM CDT | Wind Advisory | LOT | 30 hr |
| Nov 10, 2:58 AM CST | Wind Advisory | LOT | 24 hr |
| Nov 10, 1:28 PM CST | Mesoscale Discussion | SPC | 92 min |
| Nov 10, 2:05 PM CST | Tornado Watch | SPC | 6 hr |
| Nov 10, 4:34 PM CST | Severe Thunderstorm Warning | LOT | 71 min |
| Nov 10, 5:03 PM CST | Mesoscale Discussion | SPC | 57 min |
| Nov 14, 3:04 AM CST | Wind Advisory | LOT | 41 hr |
| Nov 18, 2:15 PM CST | Wind Advisory | LOT | 26 hr |
| Dec 23, 2:32 AM CST | Wind Advisory | LOT | 25 hr |
| Dec 28, 3:04 PM CST | Winter Weather Advisory | LOT | 39 hr |
| Dec 29, 3:52 PM CST | Mesoscale Discussion | SPC | 4 hr |
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20192021
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. Warning verification from the Mesonet's Cow. Rebuilt daily.