KSEA — Seattle–Tacoma International Airport
fog forecast & climatology · Seattle city page · full 10-year analysis →
Fog unlikely through Friday (peak 4%). September typically brings about 2 hours of dense fog here.forecast cycle 2026-09-04T13:00:00Z · page rebuilt daily · live layers below update hourly
- Fog hours per year
- 85 h below CAT I minima (2016–2026 average)
- Fog season
- January and December
- Typical fog event
- ~2 h once it forms (middle half 1–4 h, n=290)
- Data through
- 2026-08-15 · machine-readable data.json
When this airport fogs in
In a typical year Seattle–Tacoma International Airport spends 85 hours below CAT I approach minima (visibility under ~½ mile or ceiling under 200 ft), concentrated in January and December. The strip above shows the hour-by-hour pattern for the current month from ten years of weather observations.
Fog season
Fog season runs October through January, peaking in January; fog is mostly a 2 AM–9 AM phenomenon; typically thinning out by 11 AM; a typical event lasts about 2 hours once it forms local time · 10-yr average
Runway infrastructure
| end | approach lights | best approach | length | RVR |
|---|---|---|---|---|
| 16C | ALSF-2 | CAT IIIB | 9,426 ft | RVR |
| 34C | MALSR | CAT I | 9,426 ft | RVR |
| 16L | ALSF-2 | CAT III | 11,901 ft | RVR |
| 34R | MALSR | CAT I | 11,901 ft | RVR |
| 16R | ALSF-2 | CAT III | 8,500 ft | RVR |
| 34L | MALSR | CAT I | 8,500 ft | RVR |
From FAA NASR / curated AIP Canada research. Approach-light class and minima tier drive how low an approach can be flown — details in the chase board.
For flight operations
EFVS crews: the CHASE board ranks airports by live fog status, approach lighting, go-around height and flight time from your base. Forecast probabilities publish here per-airport once the calibrated model beats climatology on live verification — receipts on the scorecard. Methodology.
Sources: NOAA/NWS National Blend of Models guidance · METAR observations 2016–2026 (Iowa Environmental Mesonet) · FAA NASR. Machine access: data.json · llms.txt. Not for operational use.