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The climate of the city of Rio de Janeiro is tropical with a hot, humid and sometimes rainy summer and a mild and dry winter. In December and January, the heat and humidity are usually constant, reaching up to 45°C, However, it rains less in Rio de Janeiro than in other cities in the Southeast (for example, São Paulo) and the rains are usually sudden and rapid, giving a welcoming relief from the sizzling afternoon temperatures. During winter in the southern hemisphere, temperatures in Rio are usually milder. In these months rainfall decreases, and average temperatures are typically 19°C to maximums of 26°C.

Rio forum regulars describe January's rain as a nighttime event more than a daytime one: “rain in January falls in torrential downpours at night,” sometimes dumping a month's worth in a single night, and these are “summer rains” that typically arrive late in the afternoon or early at night, after a hot day of sunshine. Days themselves run genuinely hot and humid — some posters cite “around 40°C,” others closer to 35°C — and January is peak high season, so “you'll pay top dollar for just about everything.” For anyone with flexible dates, May gets named as the better alternative: warm, sunny, cooler breezes, lower humidity. Our record: 31.4°C days, feels-like 37°C, 232.9mm of rain and 18.2 rain days — hot, humid and genuinely one of the wettest months, backing the “brutal January, better in May” read.

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.

May is the local secret: 26°C, dry, the sea still warm, and Ipanema without the New Year crowd. Summer here (January) is a humid 38°C that flattens you before noon whatever the beach photos suggest.

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.

It's winter in Rio, and the forum's regulars are clear that means dry and mild rather than cold — sightseeing weather, not beach weather. The water stays cool most of the year regardless, so July doesn't lose much on that front.

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.