Table 1: Seasonality Index (SI) classes.

Rainfall Regime SI
Very equable (Rainfall spread throughout the year) < 0.19
Equable but with a definite wetter season 0.20 ± 0.39
Rather seasonal with a short drier season 0.40 ± 0.59
Seasonal 0.60 ± 0.79
Markedly seasonal with a long drier season 0.80 ± 0.99
Most rainfall in 3 months or less than that 1.00 ± 1.19
Extreme seasonality (almost all rain in 1± 2 months) > 1.20

(Ref: Kanellopoulou 2002)