Table 2.

Alternative categorization of the severity of wet and dry events often used for SPEI values.

Index value	Categorization	Probability [%]
≥2.33	extremely wet	1
1.65 to 2.32	severely wet	4
1.28 to 1.64	moderately wet	5
0.84 to 1.27	mildly wet	10
−0.83 to 0.83	near-normal	60
−1.27 to −0.84	mildly dry	10
−1.64 to −1.28	moderately dry	5
−2.32 to −1.65	severely dry	4
≤ − 2.33	extremely dry	1