| Month ↓ Station → | Bujumbura-Airport | Gitega-Zege | Imbo-SEMS | Musasa | Ruvyironza | Rwegura |
| January | 0.437 | 0.412 | 0.395 | 0.435 | 0.366 | 0.365 |
| February | 0.508 | 0.427 | 0.442 | 0.516 | 0.388 | 0.456 |
| March | 0.487 | 0.425 | 0.455 | 0.495 | 0.410 | 0.389 |
| April | 0.519 | 0.418 | 0.468 | 0.500 | 0.406 | 0.313 |
| May | 0.621 | 0.530 | 0.546 | 0.586 | 0.513 | 0.362 |
| June | 0.759 | 0.682 | 0.661 | 0.765 | 0.655 | 0.569 |
| July | 0.752 | 0.782 | 0.666 | 0.803 | 0.679 | 0.660 |
| August | 0.711 | 0.699 | 0.647 | 0.773 | 0.614 | 0.593 |
| September | 0.602 | 0.520 | 0.554 | 0.664 | 0.521 | 0.504 |
| October | 0.547 | 0.498 | 0.509 | 0.519 | 0.470 | 0.464 |
| November | 0.456 | 0.387 | 0.399 | 0.489 | 0.352 | 0.348 |
| December | 0.485 | 0.429 | 0.409 | 0.481 | 0.345 | 0.409 |
| Annual mean | 0.573 | 0.518 | 0.513 | 0.586 | 0.476 | 0.453 |