State | Description | Criterion | Probability (%) |
0 | Non-drought | SDI ≥ 0.0 | 50.0 |
1 | Mild drought | −1.0 ≤ SDI < 0.0 | 34.1 |
2 | Moderate drought | −1.5 ≤ SDI < −1.0 | 9.2 |
3 | Severe drought | −2.0 ≤ SDI < −1.5 | 4.4 |
4 | Extremely drought | SDI < −2.0 | 2.3 |