Buenos Aires or Rio de Janeiro: which climate?
Buenos Aires (Argentina) has a humid subtropical climate, whereas Rio de Janeiro (Brazil) has a tropical monsoon 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 Buenos Aires and to Rio de Janeiro.
Rio de Janeiro is warmer than Buenos Aires by 6.2 °C in annual average: 23.4 °C against 17.2 °C.
Rio de Janeiro gets more rain than Buenos Aires: 1,270 mm per year against 992 mm.
Rio de Janeiro has warmed by +1.5 °C between 1940 and 2025, against +0.6 °C in Buenos Aires. Rio de Janeiro is therefore warming faster than Buenos Aires. Both trends are statistically significant.
Buenos Aires averages 11 hot days (≥ 30 °C) and 0 frost days per year; Rio de Janeiro averages 57 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 | Buenos Aires | Rio de Janeiro | Difference |
|---|---|---|---|
| Mean daily temperature | 17.2 °C | 23.4 °C | +6.2 °C |
| Average daily high | 20.4 °C | 26.5 °C | +6.1 °C |
| Average daily low | 14.2 °C | 20.9 °C | +6.7 °C |
| Annual rainfall | 992 mm | 1,270 mm | +278 mm |
| Sunshine / day | 9.6 h | 9.6 h | negligible |
| Hot days (≥ 30 °C) | 11 d/yr | 57 d/yr | +46 d/yr |
| Frost days (< 0 °C) | 0 d/yr | 0 d/yr | negligible |
| Rainy days (≥ 1 mm) | 93 d/yr | 157 d/yr | +64 d/yr |
| Mean relative humidity | 75 % | 81 % | +6 % |
| Average peak wind | 22.6 km/h | 16.9 km/h | -5.7 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.