Red Flag Warning/National Fire Danger Rating System

August 30th, 2018


Tahoe Fire and Fuels Team

For Immediate Release

August 30, 2018

Red Flag Warning/National Fire Danger Rating System

Fire prevention is everyone’s responsibility!

Contact:  Lisa Herron, U.S. Forest Service, 530-543-2815 or Eric Guevin, Tahoe Douglas Fire Protection District, 775-588-3591

LAKE TAHOE, Calif./Nev. – Over the last several months there has been a great deal of wildland fire activity around the region.  Sadly, most fires are human-caused and completely preventable if the public would take the time to better understand conditions that are favorable for fire starts.  Fire prevention is the key to keeping our communities and forests safe from wildfire.

Although fire season is now considered a year-round event, wildfires mostly occur in the late summer and early fall when temperatures are still high, humidity is low and vegetation that can feed a wildfire is extremely dry.

These types of conditions prompted the U.S. Forest Service Lake Tahoe Basin Management Unit (LTBMU) to declare fire restrictions in effect for National Forest lands in the Tahoe Basin beginning in mid-August and continuing through November 15, 2018.  Fire restrictions mean campfires are only allowed in campgrounds that have an onsite host and other fire-related activities are prohibited.  For complete information on Lake Tahoe fire restrictions, visit the LTBMU website at

In addition to fire restrictions, which are implemented to help keep our communities and forests safe, the National Weather Service issues Red Flag Warnings and Fire Weather Watches to alert fire departments and the public about critical fire weather and dry conditions that could lead to an increase in wildfire activity.  The type of weather conditions that can cause a watch or warning include low relative humidity, strong winds, dry vegetation that can feed wildfires and the possibility of lightning strikes.  Below is an explanation of the difference between a watch and a warning:

  • Fire Weather Watch - A Fire Weather Watch is issued when fire weather conditions could exist in the next 12-72 hours.  A watch is one level below a warning, but keep in mind, fire danger remains high.
  • Red Flag Warning - A Red Flag Warning is issued for weather events, which may result in extreme fire behavior that may occur within the next 24 hours.  A Red Flag Warning is the highest alert.  During these conditions, extreme caution is urged by the public because a simple spark can cause a major wildfire.

In addition to Red Flag Warnings and Fire Weather Watches, the National Fire Danger Rating System (NFDRS) allows fire managers to estimate daily fire danger for a given area.  NFDRS uses five different color-coded adjective ratings to help the public understand fire potential:  Low, Moderate, High, Very High and Extreme.  These signs are placed in key locations to alert the public about current fire danger and are most often associated with Smokey Bear.  Below is a brief explanation of the different fire danger levels:

  • Fire Danger Level: Low (Green)

When fire danger is "low" it means vegetation that can feed a wildfire does not ignite easily from small embers, but a more intense heat source, such as lightning, may start fires in duff or dry rotten wood.  Fires in open, dry grasslands may burn easily, but most wood fires will spread slowly, creeping or smoldering.  Control of fires is generally easy.

  • Fire Danger Level: Moderate (Blue)

When fire danger is "moderate" it means fires can start from most accidental causes, but the number of fire starts is typically low.  If a fire does start in an open, dry grassland, it will burn and spread quickly on windy days.  Most wood fires will spread slowly to moderately.  Average fire intensity will be moderate except in heavy concentrations of vegetation that can feed a wildfire, which may burn hot.  Fires are still not likely to become serious and are often easy to control.

  • Fire Danger Level: High (Yellow)

When fire danger is "high” fires can start easily from most causes and small vegetation that can feed a wildfire (such as grasses and needles) will ignite readily.  Unattended campfires and brush fires are likely to escape.  Fires will spread easily, with some areas of high-intensity burning on slopes or concentrated vegetation.  Fires can become serious and difficult to control unless they are put out while still small.

  • Fire Danger Level: Very High (Orange)

When fire danger is "very high" fires will start easily from most causes.  The fires will spread rapidly and have a quick increase in intensity, right after ignition.  Small fires can quickly become large fires and exhibit extreme fire behavior, such as long-distance spotting and fire whirls.  These fires can be difficult to control and will often become much larger and longer-lasting fires.

  • Fire Danger Level: Extreme (Red)

When the fire danger is "extreme" fires of all types start quickly and burn intensely.  All fires are potentially serious and can spread very quickly with intense burning.  Small fires become big fires much faster than at the "very high" level.  Spot fires are probable, with long-distance spotting likely.  These fires are very difficult to fight and may become very dangerous and often last for several days, weeks or months.

It's important that all residents and visitors educate themselves about wildfire prevention, share the information with family and friends, and take steps to prevent a wildfire from sparking.  One less spark means one less wildfire!  For tips on preventing wildfires, visit