| Minimum (14 o’clock) relative humidity (%) | Forest fire risk weather index |
| ≥90 | 0 |
| 80 - 89 | 1 |
| 70 - 79 | 2 |
| 60 -69 | 4 |
| 50 - 59 | 8 |
| 40 - 49 | 12 |
| 30 - 39 | 16 |
| ≤29 | 20 |