Fog in Great Falls, MT

daily fog outlook & 2016–2026 climatology
Fog unlikely through Sunday (peak 2%). August typically brings about 1 hour of dense fog here.forecast cycle 2026-08-16T00:00:00Z · page rebuilt daily · live layers below update hourly

Measured at Great Falls International Airport (KGTF). Forecast percentages for this station have passed live verification.

Measuring station

stationairportfog hours/yrforecast
KGTFGreat Falls International Airport49 h/yrlive forecast

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 Great Falls fogs in

Fog here concentrates in March and December — about 49 hours in a typical year at KGTF, usually lasting ~2 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the KGTF station page.

Fog season

January: ~4 hJanFebruary: ~7 hFebMarch: ~12 hMarApril: ~5 hAprMay: ~1 hMayJune: ~1 hJunJuly: ~0 hJulAugust: ~1 hAugSeptember: ~1 hSepOctober: ~4 hOctNovember: ~4 hNovDecember: ~9 hDec
Fog season runs October through April, peaking in March; fog is mostly a 4 AM–9 AM phenomenon; typically thinning out by noon; 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.