Red Flag Warnings: Critical Fire Weather Conditions

Thursday, May 17, 2018

A Red Flag Warning is issued by the National Weather Service (NWS) when weather conditions exist for destructive or rapidly spreading fires. In many cases, fire departments rely on these warnings to make sure firefighters and resources are readily available if a fire were to break out. If you are living in the area where a warning is issued, please use extreme caution or avoid activities that could ignite a wildfire (e.g. discarding cigarettes butts, operating equipment in grassy areas, and open burning of any kind).  

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Fire weather watch

A Fire Weather Watch is a step below a Red Flag Warning. This forecast typically looks ahead 24 - 72 hours for conditions that are “favorable” for wildfire ignition. For example, in the fall and spring, some areas of the state often lack adequate moisture and experience mild drought conditions. The NWS uses these local conditions, but factors in wind speeds, humidity, temperature, and a fire danger rating to help predict the likelihood a wildfire could start.

Fire weather forecasts

A Fire Weather Forecast is a detailed listing of all the conditions that could exist or contribute to a wildfire. Below are a few factors used by the NWS to determine fire danger in its forecast:

Relative Humidity: 

  • Anything less than 20 percent is considered dry enough to assist in the ignition of wildland fire.


  • Sustained winds over 15 mph are likely to fan any flames, causing fires to rapidly expand.


  • 75º F and above also receive attention because this helps dry out forest fuels quicker.

When these three conditions exist, the potential of a fire starting and spreading is very high. Extreme care must be utilized by all to prevent ignition of a wildfire.

When a Warning is Issued

  • If planning a prescribed burn, immediately cancel the planned operations; do not burn when Red Flag Warnings are issued.
  • If pulling a trailer, make sure no chains are dragging; sparks from dragging chains will ignite a fire. 
  • Dispose of cigarettes properly; do not drop lit cigarettes on the ground or throw them out the window.
  • Do not use fireworks. 
  • Pay close attention when using firearms or target shooting.
  • Avoid any mowing on red flag days: 
    • If you must mow do so before 10 a.m. when grass is moist.
    • Watch the area for at least an hour after mowing to make sure a fire does not start.
  • Avoid leaving equipment on areas with dry vegetation.
  • Avoid parking vehicles on dry vegetation, it is best to park on bare soil or paved surfaces.
  • Make sure chainsaws and other equipment have spark arresters.
  • Pay attention to trail or park closures: 
    • If the area is closed, it is closed for a reason, please respect the closure
  • Pay attention to other restrictions such as "no open fires."
  • Avoid using charcoal or gas grills.

Fire weather resources

Several forecasting maps are available courtesy the National Weather Service (NWS). Maps are updated by NWS periodically throughout the day. Please check the time stamp on each map to determine when it was last issued.

View the maps