SPI Value | Class |
2.0+ | Extremely wet |
1.5 to 1.99 | Very wet |
1.0 to1.49 | Moderately wet |
−0.99 to 0.99 | normal |
−1.0 to1.49 | Moderately dry |
1.5 to −1.99 | Very dry |
−2.0+ | Extremely dry |