Rio de Janeiro (Rio) weather in December

Regulars call this the start of fall, meaningfully cooler and less humid than the January-March peak, sitting at the tail end of the rainy season - though they're candid Rio's own weather patterns are notoriously unpredictable, with forecasts here not particularly trustworthy even a few days out. Our row backs the still-warm, still-humid read, 29.3C reading as a hot 33C at 80 percent humidity, over 22C nights, with a real 104.4mm of rain across 12.1 days. Regulars are specific the sea itself never gets genuinely warm here, not even at the height of summer, so April's slightly cooler water isn't much of a departure from the norm. The sea sits at 25.3C. The record: 9.2 hours of sun, a 10.1 kph wind and AQI 85.

Winter here is the clearer half of the year and regulars recommend it for exactly that: fewer wet days, quieter beaches, low-season prices, and days still warm enough to lie on the sand. Our row gives 26.9C by day reading as 28C, with 35.6mm of rain across 7.4 days - a third of what the summer brings. The catch is the evening, which drops to 18.9C and wants a layer, and the sun, which manages only 8.6 hours inside 10.8 of daylight, so the beach day is short. On the water they are blunt and our column agrees: at 23C the sea is cold here in any season. The record: humidity 79 percent, a 9.5 kph wind and AQI 84.

September opens the Rio spring and regulars sell it on two things at once: beach temperatures by day with comfortable nights, and beaches that are not crowded because this is low season. They put the month at 22 to 30C with little rain and some of the clearest blue skies of the year - useful when the thing you have come to see is on top of a mountain. Our row gives 28.5C reading as 31C, 59.9mm across 8.5 days and 9.1 hours of sun. The sea is cooler now at 23.3C. The record: 20.1C nights, humidity 74 percent, a 12.4 kph wind and AQI 70.

Rio forum regulars call November one of the year's best months: late spring, “very hot (25-38°C), but not wet season yet,” with “sunny days with clean skies” and only occasional, rarely heavy showers. Rain is real but not a pattern-breaker — “very rare to see many rainy days in a row,” with a more typical week running clear days punctuated by evening storms rather than washed-out afternoons. Beach conditions get singled out as genuinely good this month, humidity still low compared to full summer, which is why regulars rate November alongside May as the pick of the year. Our record: 28°C days, 20.9°C nights, 17.6 rain days and a 25°C sea — warm and swimmable with real but not dominant rain, matching the “best of both seasons” read the forum gives November.