Illinois dense fog advisories
There are no dense fog advisories in Illinois right now. The last one was issued on October 23, 2026.
Fog will reduce visibility to a quarter mile or less, making driving hazardous.
Updated from the National Weather Service · lists refresh hourly; the live map loads current alerts directly from the NWS
Map data: NWS, OpenFreeMap, OpenStreetMap
Active dense fog advisories in Illinois
None right now. Other active alerts in Illinois: none.
Dense Fog Advisories in Illinois by year
Illinois averaged 78.9 dense fog advisories per year from 2016 to 2025, and has had 53 so far in 2026. The most recent was issued on October 23, 2026.
Counties with the most dense fog advisories
| County | 2016–2025 |
|---|---|
| DeKalb County | 121 |
| Kane County | 113 |
| Piatt County | 110 |
| Champaign County | 110 |
| Coles County | 110 |
| De Witt County | 109 |
| McHenry County | 109 |
| Lee County | 109 |
| Macon County | 109 |
| McLean County | 109 |
What a dense fog advisory means
Dense fog can cause chain-reaction crashes on highways because drivers suddenly lose sight of the road ahead.
More about dense fog advisories and the national map →
What to do
- Slow down, use low-beam headlights and leave plenty of distance.
- Never use high beams in fog.
More Illinois alerts
- Tornado Warnings
- Tornado Watches
- Severe Thunderstorm Warnings
- Flash Flood Warnings
- Flood Warnings
- Flood Watches
- Winter Storm Warnings
- Winter Storm Watches
- Winter Weather Advisories
- Cold Weather Advisories
- Freeze Warnings
- Frost Advisories
- Heat Advisories
- Extreme Heat Warnings
- High Wind Warnings
- Wind Advisories
- Red Flag Warnings
- All Illinois alerts