Frost is a threat to sensitive plants. A freeze is colder and lasts longer. Cover or bring in plants for an advisory, and protect plants, pets and pipes for a freeze warning.
| Alert | Meaning (NWS) | Note |
|---|---|---|
| Frost Advisory | Frost expected or occurring, a threat to sensitive vegetation | Frost forms when surfaces fall below 32°F; it often happens when air temperatures are in the mid-30s |
| Freeze Watch | Potential for significant, widespread freezing temperatures within 24 to 36 hours | Autumn to the end of the growing season, and in spring at its start |
| Freeze Warning | Temperatures forecast below 32°F for a long period | Below 28°F for a long time can kill most commercial crops |
Frost advisory
The National Weather Service says a Frost Advisory means areas of frost are expected or occurring, posing a threat to sensitive vegetation. Frost is thin ice crystals that form on surfaces when they drop below 32°F, much as dew forms. The NWS says it often occurs when air temperatures are in the mid-30s.
Freeze watch and freeze warning
A Freeze Watch is issued when there is a potential for significant, widespread freezing temperatures in the next 24 to 36 hours. It is used in autumn through the end of the growing season and in spring at the start of it. A Freeze Warning is issued when temperatures are forecast to drop below 32°F for a long period.
Frost, freeze and killing frost
Frost matters mainly during the growing season. The NWS calls a severe frost that ends or delays the season a "killing frost". It says that temperatures below 28°F for an extended period can kill most types of commercial crops and residential plants.
The numbers vary by office
NWS Baltimore/Washington issues a Frost Advisory when the minimum temperature is forecast at 33 to 36°F on clear, calm nights in the growing season. Other forecast offices use their own criteria, so rely on the text of the alert for your area.
What to do
For a frost advisory, cover or bring in sensitive plants. For a freeze warning, also protect pets and exposed pipes. Read the alert text for the area and time it covers.
Check your own location
See current official alerts and the impact for your ZIP code.
Common questions
What is the difference between a frost advisory and a freeze warning?
A frost advisory is for frost that threatens sensitive vegetation. A freeze warning is for temperatures forecast below 32°F for a long period, which is colder and lasts longer.
Is there a frost warning?
The National Weather Service page on cold-weather alerts lists a Frost Advisory, a Freeze Watch and a Freeze Warning, and does not list a product called a frost warning.
How cold is a frost advisory?
The NWS says frost forms when surfaces fall below 32°F and often occurs when air temperatures are in the mid-30s. One office, NWS Baltimore/Washington, issues a Frost Advisory for forecast minimum temperatures of 33 to 36°F. Other offices set their own criteria.
Sources
- NWS: Cold Weather Watches, Warnings and Advisories
- NWS: Ice and Frost
- NWS Baltimore/Washington: Watch/Warning/Advisory Definitions
Reviewed by the Storm Incoming editorial team on October 27, 2026. Follow local emergency officials if their instructions differ.