Table 4: A classification of the SPI that classifies the SPI into extreme, severe, and moderate classes for both wet and dry moisture condition.

SPI value Drought class More than +2.00 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 Less than −2.00 Extremely dry