According to the National Weather Service, here are the differences between Fire Weather Watches, Red Flag Warnings, and Extreme Fire Behavior:
Red Flag Warning: Take Action. Be extremely careful with open flames. NWS issues a Red Flag Warning, in conjunction with land management agencies, to alert land managers to an ongoing or imminent critical fire weather pattern. NWS issues a Red Flag Warning when fire conditions are ongoing or expected to occur shortly.
Fire Weather Watch: Be Prepared. A Watch alerts land managers and the public that upcoming weather conditions could result in extensive wildland fire occurrence or extreme fire behavior. A watch means critical fire weather conditions are possible but not imminent or occurring.
Extreme Fire Behavior: This alert implies a wildfire likely to rage out of control. It’s often hard to predict these fires because they behave erratically, sometimes dangerously. One or more of the following criteria must be met:
- Moving fast: High rate of spread
- Prolific crowning and/or spotting
- Presence of fire whirls
- Strong convection column1
1“Understanding Wildfire Warnings, Watches and Behavior.” National Weather Service, National Oceanic and Atmospheric Administration, https://www.weather.gov/safety/wildfire-ww