NWS Jackson Keetch Byram Guidance

Keetch-Byram Index

...Drought Index Computations...

The drought index may be computed for any desired level of mean annual rainfall. But to simplify the computations, five tables of drought factors were made up. Each table covers a specified range of mean annual rainfall. The measurements needed for the drought index are the (1) the maximum air temperature (or the drybulb temperature at time of standard observation) and (2) the total rainfall for the past 24 hours.

Current Stage of Drought

Index	Stage
99	0
199	1
299	2
399	3
499	4
599	5
699	6
800	7

THE HIGHER THE VALUE, THE HIGHER THE FIRE DANGER POTENTIAL WILL BE. A VALUE ABOVE 700 IS EXTREMELY FLAMMABLE.