| SPI Value | Class |
| SPI ≥ 2.00 | Extremely Wet |
| 1.50 ≤ SPI < 2.00 | Severely Wet |
| 1.00 ≤ SPI < 1.50 | Moderately Wet |
| −1.00 ≤ SPI < 1.00 | Near Normal |
| −1.50 ≤ SPI < −1.00 | Moderate Drought |
| −2.00 ≤ SPI < −1.50 | Severe Drought |
| SPI < −2.00 | Extreme drought |