Chandler Burning Index Description

< 50
50 - 75
75 - 90
90 - 97.5
< 97.5

Current Chandler Burning Index: LOW (29.02) Chandler Burning Index: 29.02 (on a scale of 100)
Fire Danger: LOW

The Chandler Burning Index (CBI) uses the air temperature and relative humidity to calculate a numerical index of fire danger. The CBI is based solely on weather conditions, with no adjustment for fuel moisture. That number is then equated to an «Adjective Fire Danger Severity» of either low, moderate, high, very high or extreme.

Here at Tzouhalem-Maple Bay Weather, the Chandler Burning Index (CBI) is calculated from the current weather conditions and reflects the current calculated fire danger.

Chandler Burning Index (CBI) provides a measure of the effects of average daily temperature and humidity on fire intensity and rate of spread. Both the intensity and spread components of the CBI are linearly related to temperature (an increase in temperature results in a proportionately index), but are exponentially related to humidity (a small decrease in humidity results in a large increase in the index).

The modified version of the Chandler Burning Index is computed from the following formulas:

Daily CBI ratings:
Daily = (0.0167 * (104.5 - (1.373 * RH) + (0.54 * T) ) * (124 * (-0.0142 * RH)10) )

Averaged 30 day historical CBI rating:
Monthly = ( ( (110 - 1.373 *RH) - 0.54 * (10.20 - T) ) * (124 * (-0.0142 * RH)10) ) /60

  • RH = forecasted mean afternoon relative humidity (percent)
  • T = forecasted mean afternoon temperature (degrees Celsius)

The Chandler Burning Index has been shown to be highly correlated with fire activity.

Fire Danger Rating
and Color Code
Low (L)
(Light Blue or Green)
Fuels do not ignite readily from small firebrands although a more intense heat source, such as lightning, may start fires in duff or punky wood. Fires in open cured grasslands may burn freely a few hours after rain, but woods fires spread slowly by creeping or smoldering, and burn in irregular fingers. There is little danger of spotting.
Moderate (M)
Fires can start from most accidental causes but, with the exception of lightning fires in some areas, the number of starts is generally low. Fires in open cured grasslands will burn briskly and spread rapidly on windy days. Timber fires spread slowly to moderately fast. The average fire is of moderate intensity, although heavy concentrations of fuel, especially draped fuel, may burn hot. Short-distance spotting may occur, but is not persistent. Fires are not likely to become serious and control is relatively easy.
High (H)
All fine dead fuels ignite readily and fires start easily from most causes. Unattended brush and campfires are likely to escape. Fires spread rapidly and short-distance spotting is common. High-intensity burning may develop on slopes or in concentrations of fine fuels. Fires may become serious and their control difficult unless they are attacked successfully while small.
Very High (VH)
Fires start easily from all causes and, immediately after ignition, spread rapidly and increase quickly in intensity. Spot fires are a constant danger. Fires burning in light fuels may quickly develop high intensity characteristics such as long-distance spotting and fire whirlwinds when they burn into heavier fuels.
Extreme (E)
Fires start quickly, spread furiously, and burn intensely. All fires are potentially serious. Development into high intensity burning will usually be faster and occur from smaller fires than in the very high fire danger class. Direct attack is rarely possible and may be dangerous except immediately after ignition. Fires that develop headway in heavy slash or in conifer stands may be unmanageable while the extreme burning condition lasts. Under these conditions the only effective and safe control action is on the flanks until the weather changes or the fuel supply lessens.