METAR is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.
METARs can be expressed concisely using so-called aviation flight categories, which indicates what classes of flight can operate at each airport by referring to the visibility and ceiling in each METAR. Four categories are used:
| Category | Visibility | Ceiling |
|---|---|---|
| VFR | > 5 mi | and > 3,000 ft |
| Marginal VFR | Between 3 and 5 mi | and/or Between 1,000 and 3,000 ft |
| IFR | 1 mi or more but less than 3 mi | and/or 500 ft or more but less than 1,000 ft |
| Low IFR | < 1 mi | and/or < 500 ft |