Rio de Janeiro vs Buenos Aires

Based on sunshine hours, rain days, comfortable temperatures, and humidity levels, Buenos Aires edges ahead as the better destination in September. Buenos Aires offers 9 hours of daily sunshine with only 7 rain days, while Rio de Janeiro sees 9 sunshine hours and 11 rain days.

Rio de Janeiro sits in the comfortable travel range at 27°C. Buenos Aires is also comfortable at 17°C.

For travelers who prioritize dry weather, Buenos Aires is the stronger choice in September.

Rio de Janeiro reaches an average high of 27°C (81°F) and drops to 19°C (66°F) at night during September. The daily temperature range is 8°C, meaning moderate variation throughout the day.

Buenos Aires averages 17°C (63°F) for the high and 11°C (52°F) for the low, with a daily range of 6°C. There is a notable 10°C gap between the two cities, so expect a very different feel.

Both cities are in the Southern Hemisphere, so they share the same seasonal pattern in September.

Rio de Janeiro receives approximately 88 mm of rainfall across 11 rain days during September. You can expect rain roughly every other day.

Buenos Aires sees 79 mm over 7 rain days. That makes Buenos Aires the drier option by 4 rain days and 9 mm of total precipitation.

Humidity also differs: Rio de Janeiro averages 78% while Buenos Aires sits at 70%. Rio de Janeiro will feel muggier, especially at higher temperatures.