Red Flag Warning: In Plain Words

The two fire weather alerts, as the NWS lists them

The NWS lists these products on its “Understanding Wildfire Warnings, Watches and Behavior” page:

• Red Flag Warning: Take Action.
• Fire Weather Watch: Be Prepared.

That order — Watch first in time, Warning when the pattern is here or close — is the order the NWS itself puts on the two headings.

Red Flag Warning: Take Action

The NWS says it issues a Red Flag Warning, in conjunction with land management agencies, to alert land managers to an ongoing or imminent critical fire weather pattern.

The NWS also says, in its own words, when a Red Flag Warning is issued: the NWS issues a Red Flag Warning when fire conditions are ongoing or expected to occur shortly.

Under that heading, the NWS adds this line: “Be extremely careful with open flames.”

In plain words: the critical fire weather pattern is not just possible — it is ongoing, or it is imminent, meaning about to happen. That is why a Warning is headed “Take Action” by the NWS.

Fire Weather Watch: Be Prepared

The NWS says a Watch alerts land managers and the public that upcoming weather conditions could result in extensive wildland fire occurrence or extreme fire behavior.

The NWS also says, in its own words, what a Watch means: a watch means critical fire weather conditions are possible but not imminent or occurring.

A Watch is headed “Be Prepared” by the NWS, because the conditions are upcoming and possible — not yet the ongoing or imminent pattern a Warning describes.

Who these alerts are written for

The national Red Flag Warning wording is aimed at land managers: the NWS says the Warning is issued to alert land managers, and the Watch wording names land managers and the public together.

The NWS wildfire safety page says NOAA’s National Weather Service works in conjunction with federal and state wildland managers to protect lives and property in and around America’s wildlands.

So when you see one of these alerts for your area, read it as a fire weather alert built with land management agencies — not as a general storm alert.

Extreme fire behavior, in the NWS’s words

The same national page also lists “Extreme Fire Behavior.” It says this alert implies a wildfire likely to rage out of control, and that it is often hard to predict these fires because they behave erratically, sometimes dangerously.

The page lists signs that go with it, in words and without trigger numbers: moving fast, with a high rate of spread; prolific crowning and/or spotting; presence of fire whirls; and a strong convection column.

The difference, in one look

• Fire Weather Watch: upcoming weather conditions could result in extensive wildland fire occurrence or extreme fire behavior; critical fire weather conditions are possible but not imminent or occurring.
• Red Flag Warning: an ongoing or imminent critical fire weather pattern; fire conditions are ongoing or expected to occur shortly.

Watch means possible. Warning means ongoing or imminent. That order — Be Prepared, then Take Action — is the order the NWS itself puts on the two headings.

Why no wind or humidity number is printed here

The exact numbers that trigger a Fire Weather Watch or a Red Flag Warning — the wind speeds, the humidity levels, and how long they must last — are set locally. They vary by forecast office and by fire weather zone.

That is why this page does not print one nationwide wind number, humidity number, or timing number for these alerts. Different local offices use different local criteria, because local land, fuels, and weather patterns differ. Use the alert and the criteria from your own local Forecast Office for the numbers that apply where you live.