Rome or Sydney: which climate?
Rome (Italy) has a hot-summer mediterranean climate, whereas Sydney (Australia) has a temperate oceanic climate, according to the Köppen-Geiger classification.
The values compared here are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme. The same method and the same period apply to Rome and to Sydney.
Sydney is warmer than Rome by 2.5 °C in annual average: 17.7 °C against 15.2 °C.
Rome and Sydney receive comparable annual rainfall, on the order of 860 mm.
Rome has warmed by +2.0 °C between 1940 and 2025, against +1.2 °C in Sydney. Rome is therefore warming faster than Sydney. Both trends are statistically significant.
Rome averages 43 hot days (≥ 30 °C) and 17 frost days per year; Sydney averages 2 and 0.
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
| Indicator | Rome | Sydney | Difference |
|---|---|---|---|
| Mean daily temperature | 15.2 °C | 17.7 °C | +2.5 °C |
| Average daily high | 20.1 °C | 20.1 °C | negligible |
| Average daily low | 10.7 °C | 15.5 °C | +4.8 °C |
| Annual rainfall | 860 mm | 892 mm | negligible |
| Sunshine / day | 10.0 h | 10.2 h | negligible |
| Hot days (≥ 30 °C) | 43 d/yr | 2 d/yr | -41 d/yr |
| Frost days (< 0 °C) | 17 d/yr | 0 d/yr | -17 d/yr |
| Rainy days (≥ 1 mm) | 107 d/yr | 116 d/yr | +9 d/yr |
| Mean relative humidity | 74 % | 72 % | negligible |
| Average peak wind | 13.8 km/h | 25.9 km/h | +12.1 km/h |
A difference is only reported when it exceeds the resolution of the data. ERA5 is a reanalysis on a grid of about 31 km: two nearby cities often fall in the same cell, and below half a degree you are reading the grid, not the climate.