Watch, Warning, and Advisory Definitions

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 105°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 75°F". An excessive heat warning can be issued for a heat index less than 105°F when the cumulative effect of successive days of near warning heat leads to life threatening conditions.

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 75°F". A heat advisory can be issued for a heat index less than 100°F when the cumulative effect of successive days of near advisory heat leads to potentially life threatening conditions.
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.

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