SPI | VHI | IDI | Drought Classification |
>−0.5 | >40 | 6 | Normal |
−0.5 a −0.8 | 30 a 40 | 5 | Abnormally Dry |
−0.8 a −1.3 | 20 a 30 | 4 | Moderate Drought |
−1.3 a −1.6 | 12 a 20 | 3 | Severe Drought |
−1.6 a −2.0 | 6 a 12 | 2 | Extreme Drought |
<−2.0 | <6 | 1 | Exceptional Drought |