KGTF — Great Falls International Airport
fog forecast & climatology · Great Falls city page · full 10-year analysis →
Fog unlikely through Saturday (peak 3%). September typically brings about 1 hour of dense fog here.forecast cycle 2026-09-04T13:00:00Z · page rebuilt daily · live layers below update hourly
- Fog hours per year
- 49 h below CAT I minima (2016–2026 average)
- Fog season
- March and December
- Typical fog event
- ~2 h once it forms (middle half 1–3 h, n=200)
- Data through
- 2026-08-15 · machine-readable data.json
When this airport fogs in
In a typical year Great Falls International Airport spends 49 hours below CAT I approach minima (visibility under ~½ mile or ceiling under 200 ft), concentrated in March 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 April, peaking in March; fog is mostly a 4 AM–9 AM phenomenon; typically thinning out by noon; a typical event lasts about 2 hours once it forms local time · 10-yr average
Runway infrastructure
| end | approach lights | best approach | length | RVR |
|---|---|---|---|---|
| 03 | ALSF-2 | CAT III | 10,502 ft | RVR |
| 21 | — | LPV | 10,502 ft | RVR |
| 17 | — | LPV | 6,030 ft | — |
| 35 | — | LPV | 6,030 ft | — |
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.