Fog in Ottawa, ON

daily fog outlook & 2016–2026 climatology
Fog unlikely through Monday (peak 12%). 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 Ottawa Macdonald-Cartier International Airport (CYOW). Forecast percentages for this station have passed live verification.

Measuring station

stationairportfog hours/yrforecast
CYOWOttawa Macdonald-Cartier International Airport46 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 Ottawa fogs in

Fog here concentrates in November and December — about 46 hours in a typical year at CYOW, usually lasting ~2 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the CYOW station page.

Fog season

January: ~4 hJanFebruary: ~4 hFebMarch: ~4 hMarApril: ~3 hAprMay: ~2 hMayJune: ~2 hJunJuly: ~1 hJulAugust: ~2 hAugSeptember: ~3 hSepOctober: ~5 hOctNovember: ~9 hNovDecember: ~6 hDec
Fog season runs September through April, peaking in November; fog is mostly a 3 AM–9 AM phenomenon; typically thinning out by 5 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.