Frost Advisory vs Freeze Warning: In Plain Words

The names changed in 2024

The NWS says it is simplifying a suite of cold weather forecast products to improve messaging of winter hazards and provide better decision support, as part of the Hazard Simplification initiative.

The NWS says this effort integrates public and partner engagements and social science research to improve and evolve its alerting system.

On October 1, 2024, the NWS made these freeze changes:

• Hard Freeze Watches were renamed to Freeze Watch.
• Hard Freeze Warnings were consolidated into Freeze Warning.

So if an older page, a saved alert, or a search result says “Hard Freeze Watch,” read it as the product now called a Freeze Watch. If it says “Hard Freeze Warning,” read it as the product now covered by a Freeze Warning.

The three frost and freeze alerts, as the NWS lists them today

The NWS lists these products on its “Understanding Cold Weather Alerts” page, under the heading “Freeze Watch vs Warning and Frost Advisory”:

• Freeze Warning: Take Action!
• Freeze Watch: Be Prepared.
• Frost Advisory: Be Aware.

Frost Advisory: Be Aware

A Frost Advisory means areas of frost are expected or occurring, posing a threat to sensitive vegetation.

That is the NWS wording, and it carries no temperature number. In plain words: frost itself is the event here — frost expected to form on the ground and on plants — and sensitive vegetation is what is at risk.

Freeze Watch: Be Prepared

In the NWS’s substance, a Freeze Watch is issued when there is a potential for significant, widespread freezing temperatures in the coming days.

The NWS also says, in its own words, when in the year a Freeze Watch is issued:

• A Freeze Watch is issued in the autumn until the end of the growing season and in the spring at the start of the growing season.

A Watch is headed “Be Prepared” by the NWS, because the freeze is a potential — possible and widespread if it comes — not yet the expected event a Warning describes.

Freeze Warning: Take Action!

In the NWS’s substance, a Freeze Warning is issued when temperatures are forecasted to fall to freezing or below freezing for a long period of time.

The NWS says that level of cold kills some types of commercial crops and residential plants, and that still colder cold, held for an extended period of time, can kill most types of commercial crops and residential plants.

A Warning is headed “Take Action!” by the NWS — the Warning is the one for a freeze that is forecasted, not only possible.

These alerts are about plants and the growing season

The NWS cold safety page says cold weather can also affect crops. In late spring or early fall, cold air outbreaks can damage or kill produce for farmers, as well as residential plants and flowers.

The same page says freezes and their effects are significant during the growing season.

It also says each plant species has a different tolerance to cold temperatures.

So these three products are worded around vegetation: sensitive vegetation for a Frost Advisory, and commercial crops and residential plants for a Freeze Warning. They belong to the spring and fall growing seasons described above — a Freeze Watch, in the NWS’s words, is issued in the spring at the start of the growing season and in the autumn until the end of the growing season.

The difference, in one look

• Frost Advisory: areas of frost are expected or occurring, posing a threat to sensitive vegetation.
• Freeze Watch: there is a potential for significant, widespread freezing temperatures in the coming days.
• Freeze Warning: temperatures are forecasted to fall to freezing or below freezing for a long period of time, cold that can kill some types of commercial crops and residential plants.

Advisory means frost. Watch means a freeze is possible. Warning means a freeze is forecasted. That order — Be Aware, Be Prepared, Take Action! — is the order the NWS itself puts on the three headings.

Why no temperature number is printed here

The exact temperatures that trigger a Frost Advisory, a Freeze Watch, or a Freeze Warning are set locally. They vary by office, by county, and by time of season — by where a place is in its growing season.

That is why this page does not print one nationwide temperature number for these alerts, and why the NWS definitions above are given in plain words without a number where the national wording itself carries one. Use the alert and the criteria from your own local Forecast Office for the number that applies where you live.