Fog in Jämsä

daily fog outlook & 2016–2026 climatology
No fog forecast feed exists for this station. August typically brings about 14 hours of dense fog here (10-year average).

Measured at Halli Airport (EFHA). This station has climatology and live observations only.

Measuring station

stationairportfog hours/yrforecast
EFHAHalli Airport212 h/yrclimatology

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 Jämsä fogs in

Fog here concentrates in September and October — about 212 hours in a typical year at EFHA, usually lasting ~1 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the EFHA station page.

Fog season

January: ~21 hJanFebruary: ~18 hFebMarch: ~15 hMarApril: ~11 hAprMay: ~4 hMayJune: ~5 hJunJuly: ~6 hJulAugust: ~14 hAugSeptember: ~33 hSepOctober: ~32 hOctNovember: ~29 hNovDecember: ~28 hDec
Fog season runs August through April, peaking in September; fog is mostly a 1 AM–8 AM phenomenon; typically thinning out by noon; 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.