Fog in Madison, WI

daily fog outlook & 2016–2026 climatology
Fog possible — NWS guidance shows a fog signal in the next 48 hours. August typically brings about 4 hours of dense fog here.forecast cycle 2026-08-16T00:00:00Z · page rebuilt daily · live layers below update hourly

Measured at Dane County Regional Truax Field (KMSN). This station is in forecast verification — percentages publish when it clears the accuracy bar.

Measuring station

stationairportfog hours/yrforecast
KMSNDane County Regional Truax Field32 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 Madison fogs in

Fog here concentrates in December and January — about 32 hours in a typical year at KMSN, usually lasting ~2 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the KMSN station page.

Fog season

January: ~5 hJanFebruary: ~3 hFebMarch: ~2 hMarApril: ~2 hAprMay: ~1 hMayJune: ~1 hJunJuly: ~1 hJulAugust: ~4 hAugSeptember: ~4 hSepOctober: ~1 hOctNovember: ~3 hNovDecember: ~6 hDec
Fog season is January, February, March, April, August, September, November, December, peaking in December; fog is mostly a midnight–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.