Nagasaki sää — toukokuu

May in Fukuoka is the last month before the rains: Kyushu's tsuyu usually begins around 7 to 10 June, so May sits outside it and regulars call it the nicest season of the year. That does not mean dry - our row carries 172.2mm across 11.4 precipitation days - and their description of the rhythm is three days of sun then a day or two of rain. It is also warm and, this far south, humid enough that you will sweat. The packing list they give runs the whole range: short sleeves, long sleeves, a light jacket, a rain parka, waterproof shoes and a folding umbrella. Mid-May to early June is the window. The record: 24.6C days that feel like 26C, 16.4C nights, humidity 79 percent and 8.8 hours of sun.

Forum posters consistently rate April as one of the best months to visit Japan, generally warm and springlike, though posters are direct that conditions can still turn variable enough to want a coat on some days, whether from cooler temperatures or rain. Posters describe typical April days as comfortable in shirtsleeves with a light jacket in the daypack for evenings, rather than requiring a heavy winter coat, and note that on a sunny day temperatures can climb into the mid-20sC. Posters discussing Kyushu specifically, where Nagasaki sits, describe the region as reliably warm by late March into April compared with much of the rest of Japan. Posters generally rate April as a comfortable, mild time to visit Nagasaki, with a light jacket the main packing recommendation for cooler mornings and evenings.

October is widely rated one of Japan's two best months, and Kyushu — Nagasaki, Fukuoka, Kumamoto, Kagoshima — is the part of the country the forum points at when someone wants October warmth specifically. Nagasaki bears that out: days near 23°C and nights that stay unusually mild at about 18, well above what Honshu offers by then, with the sea still at 25°C. Early October runs warm and late October cools, so a light jacket for the evening covers it. The one risk worth planning around is typhoons, which can deliver a day or two of heavy rain before things return to normal.