Greenwich boasts a year-around average temperature of 10.5°C, peaking at 17.5°C in August, its warmest month, and dipping to an average low of 4.2°C in January, the coolest. Rainfall averages at 49.3mm annually, with November seeing the heaviest showers and March, April being the driest month.
Month | Temperature (Celcius) | Rainfall (mm) |
| January | 4.2 | 53.3 |
| February | 4.5 | 40.6 |
| March | 6.3 | 38.1 |
| April | 9.5 | 38.1 |
| May | 12.2 | 45.7 |
| June | 16.0 | 45.7 |
| July | 17.1 | 55.9 |
| August | 17.5 | 58.4 |
| September | 14.6 | 48.3 |
| October | 11.0 | 55.9 |
| November | 7.7 | 63.5 |
| December | 5.3 | 48.3 |