Hamilton weather by month
Hamilton runs from about 9°C in July to 20°C in January, with July the wettest month at 123 mm.
warmest month
January
20°C
coolest month
July
9°C
wettest month
July
123 mm
worst air month
November
6 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 20°C | 116 mm | 361 h | 5 |
| February | 19°C | 44 mm | 327 h | 5 |
| March | 16°C | 78 mm | 305 h | 4 |
| April | 15°C | 86 mm | 274 h | 4 |
| May | 11°C | 79 mm | 273 h | 5 |
| June | 11°C | 101 mm | 221 h | 5 |
| July | 9°C | 123 mm | 200 h | 4 |
| August | 10°C | 92 mm | 236 h | 3 |
| September | 12°C | 105 mm | 271 h | 5 |
| October | 14°C | 121 mm | 330 h | 6 |
| November | 16°C | 98 mm | 292 h | 6 |
| December | 18°C | 111 mm | 356 h | 5 |
About 3,446 hours of sun a year. Roughly 116 rainy days a year.
These are long-run climate normals, not a forecast. A given year can sit well outside them. PM2.5 is a global model: near the coast it counts sea salt as fine particulate and reads high against ground stations, sometimes by a factor of two. Use the shape of the year, not the absolute number.
where these numbers come from
- · Temperature, rainfall and sunshine: ECMWF ERA5 reanalysis climate normals via Open-Meteo (CC BY 4.0), fetched once and stored.
- · PM2.5: Copernicus CAMS reanalysis, monthly means. Modelled, not station readings; near coasts CAMS counts sea salt as PM2.5 and reads high.
Last reviewed 2026-05-24. Full method, licences and the list of sources we rejected are on the methodology page.