| SPEI value | Drought category |
| >2 | Extremely wet |
| 1.50 to 1.99 | Very wet |
| 1.0 to 1.49 | Moderately wet |
| −0.99 to 0.99 | Near normal |
| −1.0 to −1.49 | Moderately dry |
| −1.50 to −1.99 | Severely dry |
| −2 and less | Extremely dry |