Fog in Decatur, IL

daily fog outlook & 2016–2026 climatology
No fog signal in NWS guidance for the next 48 hours. August typically brings about 2 hours of dense fog here.forecast cycle 2026-08-16T00:00:00Z · page rebuilt daily · live layers below update hourly

Measured at Decatur Airport (KDEC). This station is in forecast verification — percentages publish when it clears the accuracy bar.

Measuring station

stationairportfog hours/yrforecast
KDECDecatur Airport44 h/yrverifying

Fog is measured where instruments live — airports. Hours/yr = time below CAT I approach minima (visibility under ~½ mile or ceiling under 200 ft), the aviation definition of seriously dense fog.

When Decatur fogs in

Fog here concentrates in January and February — about 44 hours in a typical year at KDEC, usually lasting ~2 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the KDEC station page.

Fog season

January: ~10 hJanFebruary: ~6 hFebMarch: ~3 hMarApril: ~2 hAprMay: ~3 hMayJune: ~1 hJunJuly: ~2 hJulAugust: ~2 hAugSeptember: ~4 hSepOctober: ~1 hOctNovember: ~5 hNovDecember: ~6 hDec
Fog season is January, February, March, May, September, November, December, peaking in January; fog is mostly a 3 AM–8 AM phenomenon; typically thinning out by 10 AM; a typical event lasts about 2 hours once it forms local time · 10-yr average

Machine access: data.json · llms.txt · forecast verification. Not for operational use.