מזג האוויר בבואנוס איירס באוקטובר

October is jacaranda month and the city is outdoors again after a grey winter. Mid-20s, long evenings, dinner at 10pm as it should be. December through February is a wet, heavy 33°C that the numbers flatter.

Regulars are specific this month often runs milder than its late-autumn calendar position suggests - one recent visitor who worried about cold found the weather close to perfect or even a touch warm, with autumn's real chill still holding off. Our row backs the mild-cool read, 18.8C over 11.8C nights feeling 9C, with 68mm of rain across 7.1 days and a real 21.8 kph wind. Regulars are consistent this isn't a particularly rainy or dreary month either, pointing to August or September as the wetter stretch by comparison, and call the real draw here noticeably thinner crowds than peak season. The sea sits at 17.6C. The record: humidity 78 percent, 7.4 hours of sun and one of the cleanest air readings in this project, AQI 36.

December opens the summer here and the board argues about the humidity rather than the heat - some compare it to a New York July, others say it is nowhere near Miami. Our column takes the second side: 64 percent humidity with a dew point of 15.3C, so 28.3C reads as 30C rather than worse. The heat builds through the month, with the worst of it after the solstice and into January and February. Early December is the recommended half. One practical note they repeat: the subway is not air-conditioned and is stuffy in summer, so buses, taxis and walking are the way about. The jacarandas have finished by now. The record: 12.1 hours of sun, a 23.7 kph wind and AQI 32.

September is the join between winter and spring here and regulars describe it as pleasant with a gap in it: warm enough by day, cool and fresh once the sun goes, so an evening layer is not optional. Our row gives 19.3C days feeling like 17C over 11.6C nights that feel like 8C, with a 24.1 kph wind doing most of that. The spring flowers are starting. The jacarandas are not - they begin in the first week of November and peak around the 15th to the 20th, so anyone booking this month for the purple streets has come six weeks early. Rain is moderate at 65.6mm across 6.1 days. The record: humidity 74 percent, 8.9 hours of sun and AQI 34.

November is the month Buenos Aires regulars name as the year's best: warm without the heat and the mugginess of January and February, which our row puts at 25.8C days and 16.9C nights. What brings people specifically in this month is the jacarandas. The consensus timetable is that they start in the first week, are at their best somewhere around the 15th to the 20th, and can still be worth seeing at the end of the month - with the standing caveat that the trees keep their own calendar and no year repeats the last. They turn whole avenues and the parks purple. Our row's 25.1 kph wind is the other November fact, and 7.7 precipitation days carry 77.6mm. The record: 11.3 hours of sun, humidity 67 percent and AQI 32.