Lisbon (Lisboa) weather in September

Regulars are specific that mid-September is a genuine turning point for crowds rather than weather: Portuguese and Spanish schools go back around then, so visitor numbers drop noticeably even as the weather itself stays warm and sunny through the month. Our row backs the pleasant, still-summery read, 27.2C reading as a real 27C, over 18.1C nights, with rain minimal at 23.9mm across 3.2 days. Regulars are consistent nights cool down enough that AC isn't really needed, a genuine comfort upside over the peak summer months. The sea sits at 19.1C, on the cool side but manageable. The record: humidity 73 percent, 10.8 hours of sun, a 22.2 kph wind and AQI 38.

Regulars are direct with anyone hoping to swim this month: air temperatures reaching the high teens or 20C don't mean the Atlantic has warmed to match, and expecting a comfortable swim based on a sunny afternoon is called out as a common, avoidable disappointment. Our row backs the mismatch, 20C reading as 19C over 12.3C nights, against a sea still at a cool 16.9C. Rain is described as short, sharp showers rather than sustained rain, matching our 58.5mm across 10.5 days, and regulars note a real 23.4 kph wind that can make an already-cool sea feel colder still on a breezy day. Layering is the standard advice, since a warm-looking afternoon can still carry a genuine chill in the wind. The record: humidity 76 percent, 11 hours of sun and AQI 43.

The sardinhas run all June - bunting across the streets, trestle tables and charcoal braziers set out by restaurants and households - but regulars are clear the month has a single night. The 12th, with the parade and the Alfama crush, is a bigger occasion here than New Year and runs until morning, with parties across Santos, Graca and Bica as well. Around it the weather is the easy part: hot without July's heat, 25.6C by day and 16.9C at night, 9.7mm of rain across 3.1 days, and 12.9 hours of sun. The Atlantic keeps the sea at 19.8C and the breeze at 24.4 kph. The record: humidity 73 percent and AQI 42.

Lisbon forum regulars describe November as unpredictable but rarely a washout: “a nice day in the sun around 15-18°C and cold rainy days around 10-12°C,” with rain typically arriving in short bursts — “20 minutes of pouring rain then 4 hours without rain, then another 20 minutes...then 2 hours of sun.” A visit might see rain roughly 5 days across two weeks, but “always in short rain showers,” with locals simply ducking into a café to wait it out rather than treating it as a lost day. The one packing note beyond a warm layer: the calçada portuguesa paving gets genuinely slippery when wet, so proper shoes matter. November is billed as off-season, though regulars note it can still feel busy at the main sights. Our record: 17.4°C days, 13.3°C nights, 10 rain days and a 22.5kph wind — mild with real, frequent rain, matching the “short bursts, not a washout” read.

Lisbon forum regulars are consistent that February is genuinely winter, if a mild one: cool and cloudy, with a chance of rain, typical daytime readings “15 to 18 degrees” and nights “5 and 10.” Days can go either way — grey, rainy and cold or sunny, blue and cold — with wind and rain the two things visitors dislike most and either (or both) fairly common. None of it reads as harsh by the forum's own comparison: “the weather here is never too cold,” a light rain coat is called sufficient, and visitors come year-round including the first week of February without much complaint. Our record: 15.6°C days, 10.2°C nights, 5 rain days and a 13.5°C sea — mild and comparatively dry, backing the “cool but never harsh” framing over the “grey and cold” half of the split.