KORD — Chicago O'Hare International Airport
fog forecast & climatology · Chicago city page · full 10-year analysis →
No fog signal in NWS guidance for the next 48 hours. dense fog (visibility under a mile) is rare here in September.forecast cycle 2026-09-04T13:00:00Z · page rebuilt daily · live layers below update hourly
- Fog hours per year
- 21 h below CAT I minima (2016–2026 average)
- Fog season
- January and December
- Typical fog event
- ~2 h once it forms (middle half 1–3 h, n=96)
- Data through
- 2026-08-15 · machine-readable data.json
When this airport fogs in
In a typical year Chicago O'Hare International Airport spends 21 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 December through March, peaking in January; fog is mostly a 11 PM–7 AM phenomenon; typically thinning out by 9 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 |
|---|---|---|---|---|
| 04L | — | — | 7,500 ft | RVR |
| 22R | MALSR | CAT I | 7,500 ft | RVR |
| 04R | MALSR | CAT I | 8,075 ft | RVR |
| 22L | MALSR | CAT II | 8,075 ft | RVR |
| 09C | ALSF-2 | CAT III | 11,245 ft | RVR |
| 27C | ALSF-2 | CAT III | 11,245 ft | RVR |
| 09L | ALSF-2 | CAT III | 7,500 ft | RVR |
| 27R | ALSF-2 | CAT III | 7,500 ft | RVR |
| 09R | ALSF-2 | CAT III | 11,260 ft | RVR |
| 27L | ALSF-2 | CAT III | 11,260 ft | RVR |
| 10C | ALSF-2 | CAT III | 10,800 ft | RVR |
| 28C | ALSF-2 | CAT III | 10,800 ft | RVR |
| 10L | ALSF-2 | CAT III | 13,000 ft | RVR |
| 28R | ALSF-2 | CAT III | 13,000 ft | RVR |
| 10R | ALSF-2 | CAT I | 7,500 ft | RVR |
| 28L | ALSF-2 | CAT III | 7,500 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.