Weather data over a 35-year period was examined to determine average Keetch-Byram drought index (KBDI) values for each region of the state on a seasonal basis. These average KBDI values are given in the following table as the "NORMAL" classification. Departures from this average value were related to fire activity to determine the breakpoints for the other classes.
( Field Units 1-7)
| WINTER | SPRING | SUMMER | FALL | |
|---|---|---|---|---|
| VERY LOW | 0-160 | 0-190 | 0-220 | 0-180 |
| LOW | 161-220 | 191-260 | 221-300 | 181-240 |
| NORMAL | 221-390 | 261-460 | 301-500 | 241-420 |
| MODERATE | 391-500 | 461-600 | 501-640 | 421-540 |
| SEVERE | 501-800 | 601-800 | 641-800 | 541-800 |
( Field Units 8-14)
| WINTER | SPRING | SUMMER | FALL | |
|---|---|---|---|---|
| VERY LOW | 0-100 | 0-200 | 0-160 | 0-160 |
| LOW | 101-180 | 201-280 | 161-240 | 161-220 |
| NORMAL | 181-400 | 281-530 | 241-460 | 221-400 |
| MODERATE | 401-540 | 531-700 | 461-620 | 401-530 |
| SEVERE | 541-800 | 701-800 | 621-800 | 531-800 |
( Field Units 15-18)
| WINTER | SPRING | SUMMER | FALL | |
|---|---|---|---|---|
| VERY LOW | 0-230 | 0-260 | 0-150 | 0-220 |
| LOW | 231-300 | 261-340 | 151-200 | 221-270 |
| NORMAL | 301-490 | 341-550 | 201-350 | 271-420 |
| MODERATE | 491-630 | 551-700 | 351-450 | 421-510 |
| SEVERE | 631-800 | 701-800 | 451-800 | 511-800 |