| SPI values | Category |
| 2.00 and above | Extremely wet |
| 1.50 to 1.99 | Very wet |
| 1.00 to 1.49 | Moderately wet |
| −0.99 to 0.99 | Near Normal |
| −1.00 to −1.49 | Moderately dry |
| −1.50 to −1.99 | Severely dry |
| −2.00 and less | Extremely dry |