Fog in Boston, MA

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 Boston Logan International Airport (KBOS). This station is in forecast verification — percentages publish when it clears the accuracy bar.

Measuring station

stationairportfog hours/yrforecast
KBOSBoston Logan International Airport52 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 Boston fogs in

Fog here concentrates in October and September — about 52 hours in a typical year at KBOS, usually lasting ~2 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the KBOS station page.

Fog season

January: ~3 hJanFebruary: ~4 hFebMarch: ~5 hMarApril: ~5 hAprMay: ~5 hMayJune: ~4 hJunJuly: ~4 hJulAugust: ~5 hAugSeptember: ~5 hSepOctober: ~7 hOctNovember: ~1 hNovDecember: ~4 hDec
Fog season runs December through October, peaking in October; fog is mostly a 1 AM–9 AM phenomenon; 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.