Fog in Philadelphia, PA

daily fog outlook & 2016–2026 climatology
No fog signal in NWS guidance for the next 48 hours. dense fog (visibility under a mile) is rare here in August.forecast cycle 2026-08-16T00:00:00Z · page rebuilt daily · live layers below update hourly

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

Measuring stations

stationairportfog hours/yrforecast
KPHLPhiladelphia International Airport21 h/yrverifying
KPNENortheast Philadelphia Airport38 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 Philadelphia fogs in

Fog here concentrates in January and February — about 21 hours in a typical year at KPHL, usually lasting ~1 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the KPHL station page.

Fog season

January: ~5 hJanFebruary: ~4 hFebMarch: ~2 hMarApril: ~1 hAprMay: ~1 hMayJune: ~0 hJunJuly: ~0 hJulAugust: ~0 hAugSeptember: ~0 hSepOctober: ~3 hOctNovember: ~1 hNovDecember: ~4 hDec
Fog season is January, February, March, October, December, peaking in January; fog is mostly a 1 AM–8 AM phenomenon; typically thinning out by 10 AM; a typical event lasts about 1 hour once it forms local time · 10-yr average

Machine access: data.json · llms.txt · forecast verification. Not for operational use.