Saginaw, Minnesota, USA
 Today is

MN Fire Weather
Camp Fire Smokey the Bear Forest Fire

Fwi o medium Fire Weather Index
Fwi legend
Fwi f medium
Ffmc o medium Fine Fuel Moisture Code
Ffmc legend
Ffmc f medium
Dmc o medium Duff Moisture Code
Dmc legend
Dmc f medium
Dc o medium Drought Code
Dc legend
Dc f medium
Isi o medium Initial Spread Index
Isi legend
Isi f medium
Bui o medium Buildup Index
Bui legend
Bui f medium


Fire Rating Descriptions

Fire Weather Index
LOW
0.0-4.9
MODERATE
5.0-13.9
HIGH
14.0-20.9
VERY HIGH
21.0-32.9
EXTREME
33.0+

The Fire Weather Index (FWI) is based on weather readings taken at noon standard time and rates fire danger at the mid afternoon peak from 2:00 pm to 4:00 pm.

To interpret the system, the three fuel moisture codes and the three behaviour indices need to be understood. Each code and index is a numerical rating related to likely fire behaviour. The scales start at zero, and except for the Fine Fuel Moisture Code which has a maximum of 99, all are open-ended. Low ratings indicate high moisture content, and ratings rise as moisture content decreases. Ratings rise as fire weather becomes more severe.

Weather readings required are:

  • Air temperature (in the shade)
  • Relative Humidity (in the shade)
  • Wind speed (at 33 feet above ground level for an average over 10 minutes)
  • Rainfall (For the previous 24 hours)
  • The Fire Weather Index has six components:

    Three Fuel Moisture Codes:

  • 1. Fine Fuel Moisture Code
  • 2. Duff Moisture Code
  • 3. Drought Code
  • Three Fire Behaviour Indices:

  • 1. Initial Spread index
  • 2. Build Up Index
  • 3. Fire Weather Index

  • Fine Fuel Moisture Code
    LOW
    0.0-80.9
    MODERATE
    81.0-87.9
    HIGH
    88.0-90.4
    VERY HIGH
    90.5-92.4
    EXTREME
    92.5+

    The Fine Fuel Moisture Code (FFMC) is a numerical rating of the moisture content of surface litter and other cured fine fuels. It shows the relative ease of ignition and flammability of fine fuels. The moisture content of fine fuels is very sensitive to the weather. Even a day of rain, or of fine and windy weather, will significantly affect the FFMC rating. The system uses a time lag of two-thirds of a day to accurately measure the moisture content in fine fuels. The FFMC rating is on a scale of 0 to 99. Any figure above 70 is high, and above 90 is extreme.


    Duff Moisture Code
    LOW
    0.0-12.9
    MODERATE
    13.0-27.9
    HIGH
    28.0-41.9
    VERY HIGH
    42.0-62.9
    EXTREME
    63.0+

    The Duff Moisture Code (DMC) is a numerical rating of the average moisture content of loosely compacted organic layers of moderate depth. The code indicates the depth that fire will burn in moderate duff layers and medium size woody material. Duff layers take longer than surface fuels to dry out but weather conditions over the past couple of weeks will significantly affect the DMC. The system applies a time lag of 12 days to calculate the DMC. A DMC rating of more than 30 is dry, and above 40 indicates that intensive burning will occur in the duff and medium fuels. Burning off operations should not be carried out when the DMC rating is above 40.


    Drought Code
    LOW
    0.0-79.9
    MODERATE
    80.0-209.9
    HIGH
    210.0-273.9
    VERY HIGH
    274.0-359.9
    EXTREME
    360.0+

    The Drought Code (DC) is a numerical rating of the moisture content of deep, compact, organic layers. It is a useful indicator of seasonal drought and shows the likelihood of fire involving the deep duff layers and large logs. A long period of dry weather (the system uses 52 days) is needed to dry out these fuels and affect the Drought Code. A DC rating of 200 is high, and 300 or more is extreme indicating that fire will involve deep sub-surface and heavy fuels. Burning off should not be permitt


    Initial Spread Index
    LOW
    0.0-3.9
    MODERATE
    4.0-7.9
    HIGH
    8.0-10.9
    VERY HIGH
    11.0-18.9
    EXTREME
    19.0+

    The Initial Spread Index (ISI) indicates the rate fire will spread in its early stages. It is calculated from the FFMC rating and the wind factor.

    The open-ended ISI scale starts at zero and a rating of 10 indicates high rate of spread shortly after ignition. A rating of 19 or more indicates extremely rapid rate of spread.


    Build Up Index
    LOW
    0.0-18.9
    MODERATE
    19.0-33.9
    HIGH
    34.0-53.9
    VERY HIGH
    54.0-76.9
    EXTREME
    77.0+

    The Build Up Index (BUI) shows the amount of fuel available for combustion, indicating how the fire will develop after initial spread. It is calculated from the Duff Moisture Code and the Drought Code.

    The BUI scale starts at zero and is open-ended. A rating above 34 is high, above 77 is extreme.