| RDIst | Category |
| 2 or more | Extremely wet |
| 1.5 to 1.99 | Severely wet |
| 1 to 1.49 | Moderately wet |
| 0 to 0.99 | Normal condition-wet |
| 0 to −0.99 | Normal condition-dry |
| −1 to −1.49 | Moderate drought |
| −1.5 to −1.99 | Severe drought |
| −2 or less | Extreme drought |