Table 3 SPEI classification of dry and wet conditions.

From: Integration of the reptile search algorithm and the adaptive neuro-fuzzy inference system enhances standardized precipitation evapotranspiration index forecasting

Category

SPEI

Extreme wet

SPEI \(\ge\) 2.0

Severe wet

\(1.5\le\) SPEI \(\le 2.0\)

Moderate wet

\(1.0\le\) SPEI \(\le 1.5\)

Normal

\(-1.0\le\) SPEI \(\le 1.0\)

Moderate dry

\(-1.5\le\) SPEI \(\le -1.0\)

Severe dry

\(-2.0\le\) SPEI \(\le -1.5\)

Extreme dry

\(-2.0\le\) SPEI

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