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Table 1 Precipitation excess (wet) or deficit (dry) severity class according to SPI values and corresponding D-scale

From: Spatial and temporal appraisal of drought jeopardy over the Gangetic West Bengal, eastern India

SPI values Draught severity class D-Scale
2.0+ Extremely wet W3
1.5 to 1.99 Very wet W2
1.0 to 1.49 Moderately wet W1
−.99 to .99 Near normal N
−1.0 to −1.49 Moderately dry D1
−1.5 to − 1.99 Severely dry D2
−2 and less Extremely dry D3
  1. Source: Based on the user guide of the WMO 2012 (URL: