Weather alerts in Illinois, 2015
2,921 weather alerts in 2015, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered any part of the state, so the counties below add up to more than the state.
Weather alerts by county
Each county as a circle sized by its count in 2015. Tap one for its archive.
- Alerts
- 2,921
- Warnings
- 1,433
- Watches
- 201
- Advisories
- 687
- Busiest month
- June799 alerts
- Busiest day
- June 8, 201597 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
36 of 95 tornado warnings covering Illinois in 2015 had a tornado report inside them; 83 of 125 tornado reports fell inside a warning, on average 15 minutes after it went out.
Illinois, 2015
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 95 | 36 | 62% | 125 | 66% | 15 min |
| Severe thunderstorm warnings | 501 | 252 | 50% | 809 | 69% | 21 min |
| Flash flood warnings | 206 | 92 | 55% | 169 | 77% | 107 min |
Each office's whole area, 2015
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Chicago, IL: tornado warnings | 36 | 22 | 39% | 69 | 83% | 15 min |
| NWS Chicago, IL: severe thunderstorm warnings | 147 | 73 | 50% | 252 | 71% | 20 min |
| NWS Chicago, IL: flash flood warnings | 46 | 20 | 57% | 44 | 84% | 87 min |
| NWS Indianapolis, IN: tornado warnings | 18 | 2 | 89% | 7 | 43% | 9 min |
| NWS Indianapolis, IN: severe thunderstorm warnings | 141 | 59 | 58% | 209 | 62% | 21 min |
| NWS Indianapolis, IN: flash flood warnings | 48 | 13 | 73% | 35 | 77% | 72 min |
| NWS Lincoln, IL: tornado warnings | 20 | 4 | 80% | 16 | 31% | 3 min |
| NWS Lincoln, IL: severe thunderstorm warnings | 150 | 72 | 52% | 307 | 67% | 22 min |
| NWS Lincoln, IL: flash flood warnings | 78 | 25 | 68% | 55 | 80% | 144 min |
| NWS Paducah, KY: tornado warnings | 30 | 7 | 77% | 27 | 37% | 7 min |
| NWS Paducah, KY: severe thunderstorm warnings | 172 | 79 | 54% | 194 | 70% | 18 min |
| NWS Paducah, KY: flash flood warnings | 54 | 20 | 63% | 47 | 60% | 63 min |
| NWS Milwaukee, WI: tornado warnings | 9 | 2 | 78% | 7 | 29% | 9 min |
| NWS Milwaukee, WI: severe thunderstorm warnings | 74 | 40 | 46% | 194 | 73% | 24 min |
| NWS Milwaukee, WI: flash flood warnings | 6 | 2 | 67% | 7 | 43% | 77 min |
| NWS Quad Cities, IA: tornado warnings | 25 | 8 | 68% | 42 | 50% | 17 min |
| NWS Quad Cities, IA: severe thunderstorm warnings | 131 | 86 | 34% | 316 | 72% | 20 min |
| NWS Quad Cities, IA: flash flood warnings | 30 | 23 | 23% | 60 | 88% | 65 min |
| NWS St. Louis, MO: tornado warnings | 45 | 5 | 89% | 16 | 50% | 11 min |
| NWS St. Louis, MO: severe thunderstorm warnings | 214 | 98 | 54% | 378 | 74% | 23 min |
| NWS St. Louis, MO: flash flood warnings | 96 | 41 | 57% | 126 | 83% | 176 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
2,921 alerts are too many to list on one page. Narrow it to a product above, to a month in the chart, or to a county.
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
By county
Every county with at least one alert. A county page lists each alert that covered it.
- Iroquois County209
- LaSalle County206
- Grundy County203
- Kankakee County181
- Lake County167
- Kendall County163
- Will County161
- Livingston County158
- Gallatin County158
- Pope County155
- Jackson County154
- Fulton County154
- Kane County152
- Hancock County152
- Ford County147
- Franklin County147
- Pike County147
- Johnson County145
- McDonough County145
- White County145
- Bureau County144
- Rock Island County144
- Alexander County143
- Union County143
- Tazewell County143
- Henry County141
- Saline County141
- Williamson County140
- Henderson County140
- Saint Clair County140
- Hardin County140
- DeKalb County139
- Peoria County139
- Adams County139
- DuPage County138
- Lee County137
- Putnam County137
- Mason County137
- Perry County136
- Mercer County135
62 more counties
- Warren County135
- Wabash County134
- Vermilion County134
- Pulaski County133
- Knox County133
- McLean County132
- Massac County132
- Woodford County130
- Madison County130
- McHenry County129
- Ogle County129
- Whiteside County129
- Winnebago County127
- Wayne County127
- Marshall County126
- Calhoun County126
- Hamilton County126
- Monroe County125
- Randolph County125
- Cook County124
- Boone County123
- Jefferson County123
- Champaign County119
- Logan County118
- Lawrence County116
- Piatt County116
- Cass County115
- Brown County115
- Crawford County114
- Clinton County114
- Washington County113
- Richland County112
- Morgan County112
- Jersey County112
- Clay County111
- Stark County111
- Coles County111
- Clark County111
- Carroll County110
- Edwards County109
- Macoupin County108
- Fayette County107
- Schuyler County106
- Greene County106
- Edgar County105
- Macon County105
- Scott County105
- DeWitt County104
- Menard County104
- Sangamon County103
- Moultrie County102
- Shelby County102
- Bond County102
- Marion County101
- Stephenson County100
- Jasper County100
- Montgomery County99
- Douglas County98
- Cumberland County98
- Effingham County95
- Christian County94
- Jo Daviess County92
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordThe radar archive20142016
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.