Fog in Marion, IL

daily fog outlook & 2016–2026 climatology
No fog signal in NWS guidance for the next 48 hours. August typically brings about 5 hours of dense fog here.forecast cycle 2026-08-16T00:00:00Z · page rebuilt daily · live layers below update hourly

Measured at Veterans Airport of Southern Illinois (KMWA). This station is in forecast verification — percentages publish when it clears the accuracy bar.

Measuring station

stationairportfog hours/yrforecast
KMWAVeterans Airport of Southern Illinois47 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 Marion fogs in

Fog here concentrates in November and August — about 47 hours in a typical year at KMWA, usually lasting ~1 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the KMWA station page.

Fog season

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

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