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About the MRCC Keetch-Byram Drought Index Product

The KBDI is built purely off of normal annual precipitation, daily precipitation amount and daily maximum air temperature.  Algorithms are applied to derive the daily water balance and soil moisture (assumed to have a maximum storage capacity of 8”) (Texas Weather Connection).  Unlike most drought indices that are often standardized and reflect numbers ranging from below zero (typically indicating drier conditions) to above zero (wetter conditions), the KBDI ranges from 0 to 800, where the higher the number, the drier the conditions.  Often after a minimum amount of threshold precipitation within a day, the KBDI will reset to 0.  With each dry day, the KBDI index increases.  The warmer the air temperatures, the greater potential for moisture depletion; the KBDI value will increase faster. While the KBDI could be used for any application in need of a daily indication of drought severity, it has historically been most popular within the wildfire community.

Value descriptions:

  • KBDI = 0 - 200: Soil moisture and large class fuel moistures are high and do not contribute much to fire intensity. Typical of spring dormant season following winter precipitation.
  • KBDI = 200 - 400: Typical of late spring, early growing season. Lower litter and duff layers are drying and beginning to contribute to fire intensity.
  • KBDI = 400 - 600: Typical of late summer, early fall. Lower litter and duff layers actively contribute to fire intensity and will burn actively.
  • KBDI = 600 - 800: Often associated with more severe drought with increased wildfire occurrence. Intense, deep burning fires with significant downwind spotting can be expected. Live fuels can also be expected to burn actively at these levels.

Station KBDI Data

If you would like to run Keetch-Byram Drought Index data for a single station, please visit the cli-MATE (MRCC Application Tools Environment) section of our website. KBDI data in both chart plot and tabular data value are available from menu item Station Data > Daily > Keetch-Byram Index.

References and Further Information

Alexander, M. E., 1990: Computer calculation of the Keetch-Byram drought index – Programmers Beware!  Fire Management Notes. 51(4), pp. 23-24.

Byram, G. and J. Keetch, 1988: A Drought Index for Forest Fire Control, US Dept of Agric. – Forest Service Report, SE-38, 33 pp.

Texas Weather Connection, “Keetch-Byram Drought Index (KBDI)”,, accessed June 2013.

Wildland Fire Assessment System, “Keetch-Byram Drought Index”,, accessed June 2013.

Xanthopoulos, G., G. Maheras, V. Gouma, and M. Gouvas, 2006:  Is the Keetch-Byram drought index (KBDI) directly related to plant water stress?, Internatl Conf on Forest Fire Res., D. X. Viegas (Ed.), 9 pgs