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 December. Buenos Aires offers 12 hours of daily sunshine with only 8 rain days, while Rio de Janeiro sees 10 sunshine hours and 20 rain days.

Rio de Janeiro can feel quite hot at 30°C, so plan for heat. Buenos Aires is also comfortable at 27°C.

For travelers who prioritize dry weather, Buenos Aires is the stronger choice in December. Buenos Aires receives 2 more hours of sunshine per day, which matters for sightseeing and outdoor activities.

Rio de Janeiro reaches an average high of 30°C (86°F) and drops to 23°C (73°F) at night during December. The daily temperature range is 7°C, meaning relatively stable temperatures from day to night.

Buenos Aires averages 27°C (81°F) for the high and 19°C (66°F) for the low, with a daily range of 8°C. The 3°C difference is noticeable but not dramatic.

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

Rio de Janeiro receives approximately 226 mm of rainfall across 20 rain days during December. Rain is frequent, so waterproof gear is essential.

Buenos Aires sees 88 mm over 8 rain days. That makes Buenos Aires the drier option by 12 rain days and 138 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.