Watch, Warning, and Advisory Definitions
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Non-Precipitation Definitions
For watches and warnings:
- High Wind
- Sustained non-convective winds greater than or equal to 40 mph lasting for one hour or longer, and/or gusts greater than or equal to 58 mph for any duration.
- Excessive Heat
- A heat index of 110°F or higher is expected for a period of 3 hours or more. An excessive heat warning shall be continued through the overnight hours, following a day with excessive heat, if the heat index is not expected to fall below "around 80°F".
For warnings only:
- Freeze
- Freezing temperatures (shelter temperature 32°F or below) occurs during the growing season.
For advisories:
- Dense Fog
- Widespread visibilities reduced to less than or equal to 1/4-mile in fog.
- Wind
- Sustained non‑convective winds greater than or equal to 30 mph lasting for one hour or longer, or winds greater than or equal to 45 mph for any duration.
- Heat
- A heat index of 100°F or higher is expected for a period of 3 hours or more. A heat advisory shall be continued through the overnight hours, following a day with excessive heat, if the heat index is not expect to fall below "around 80°F".
- Frost
- Conditions that would lead to frost formation during the growing season, but warmer than freezing conditions. Generally clear, calm night with shelter temperatures of 33 to 37°F.
