Fog in Marathon, ON

daily fog outlook & 2016–2026 climatology
No fog signal in NWS guidance for the next 48 hours. August typically brings about 15 hours of dense fog here.forecast cycle 2026-08-16T00:00:00Z · page rebuilt daily · live layers below update hourly

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

Measuring station

stationairportfog hours/yrforecast
CYSPMarathon Airport329 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 Marathon fogs in

Fog here concentrates in July and May — about 329 hours in a typical year at CYSP, usually lasting ~2 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the CYSP station page.

Fog season

January: ~5 hJanFebruary: ~7 hFebMarch: ~4 hMarApril: ~9 hAprMay: ~19 hMayJune: ~18 hJunJuly: ~27 hJulAugust: ~15 hAugSeptember: ~14 hSepOctober: ~4 hOctNovember: ~6 hNovDecember: ~5 hDec
Fog season is February, April, May, June, July, August, September, peaking in July; fog is mostly a 8 AM–11 AM phenomenon; typically thinning out by 6 PM; 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.