What does a “Red Flag Warning” mean? What should you do?

Updated links and republished Oct 2019.

Many residents in Sonoma County live in or near fire danger.  For those who do live in a high fire area, knowing what to do when conditions are ideal for a forest (or urban fire) is essential.

Red Flag Warning

Red Flag Smokey NM
A Red Flag Warning alert issued by the National Weather Service is a time when conditions for a fire are at the highest. Three criteria are considered prior to issuing a red flag warning. 

  • Sustained wind speeds averaging 15 mph or greater
  • Relative humidity 25% or less
  • Temperature over 75 degrees F

Fuel Moisture Index

The fuel moisture index is a tool used to understand fire potential. 10-hour fuel moisture also known as Dead Fuel Moisture; when fuel moisture is <30%, it is essentially considered dead. 10-hour fuel moisture applies to grasses and bushes up to 1 inch in diameter. Learn more at NOAA.

The US National Weather Service warning is to inform area fire fighters and land management agencies that conditions are ideal for wild-land fire combustion. Cal Fire and local fire agencies all go on a high alert status under these conditions.

The Wind Cries...Santa Ana or Diablo?

The Santa Ana and Diablo winds occur throughout the year, but are extremely dangerous during dry periods (which, in Southern CA is practically year round). Santa Ana occurs in Southern CA, Diablo in the north. Winds come from the east from hot surfaces (deserts) and are compressed and speed up as they head towards the ocean. Learn more from SFSU. Check out current wind conditions at Windy.com.

Be Prepared

Here are some things you can do when Red Flag Warnings are issued.  State and local news agencies usually announce Red Flag Warning 24-48 hours in advance on TV and radio, so there is time to act on short-term fixes. 

During Fire Season

  • Garden hose ready to use
    Garden hose ready to use
    Make sure garden hoses are hooked up and ready to use with spray nozzles attached; best practice is to never leave a garden hose randomly piled up as it will always tangle – if you want it coiled, coil it in equal sized oval loops with each successive loop offset few inches in the same direction.
  • All portable propane tanks (BBQ, smoker, etc.) should be turned off and moved away from your house.
  • If you have a pool: in an emergency, a pressure washer can be used to pump water from your pool and should be left in an available location; fire fighters should have clear access to your pool.
  • Decks should be cleared above and below of flammable objects.
  • Gas cans – for lawn mowers, chippers, whatever – should be moved away from house or garage/barn.
  • Cover firewood stacks next to house with a fire resistant cover.
  • Make sure cell phones are charged and ready for alerts and within hearing at all times.
  • Close exterior doors and windows. Leave doors unlocked. Leave lights on inside and outside of house.
  • If you have a ladder, leave it available outside, next to the house, in case fire fighters need to access roof.
  • Have all your evacuation supplies such as flashlights and a good portable radio ready to go.
  • Make sure your cars have plenty of gas and are parked outside, or garage door is capable of manual operation and all capable family members know how to open it.
  • If appropriate, shut off gas supply line at the meter.

 Ongoing Preparations 

  • Clean out the gutter
    This gutter needs some cleaning
    Make an evacuation plan and collect all necessary supplies.
  • Clean gutters and roof debris regularly.
  • Where possible, install mesh screening under decks to prevent burning material from blowing.
  • Move firewood piles away from house.
  • If you have a pool, research the special pump systems that are available for fire fighting.
  • For more information obtain a free brochure: “Living with Fire in Sonoma County” from fire agencies of Sonoma County.

Learn more about disaster preparation and recovery on Disaster Recovery Resources.

By Karen Giovannini
Contributor - Agriculture Ombudsman