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 valueDrought class

More than +2.00Extremely wet
+1.50 to +1.99Very wet
+1.00 to +1.49Moderately wet
+0.99 to −0.99Near normal
−1.00 to −1.49Moderately dry
−1.50 to −1.99Severely dry
Less than −2.00Extremely dry