ボストン 9月の天気
ボストンの9月:暖かい、雨が多い、空気がきれい — 一年で最も訪れやすい月のひとつ。
2026年9月更新 · ERA5再解析による気候平年値
ボストンでは12か月中1位 · 9月に訪れたい旅行先で1413か所中209位 · 快適スコア90/100(Sランク)
- 日中
- 24°C
- 夜
- 15°C
- 雨の日
- 7
- 日照
- 8.5 h
- 湿度
- 76%
- 日の長さ
- 13 h

9月のボストンについての旅行者の声
Boston-forum threads on September timing point past Labor Day: September 1st is the city's biggest moving day, when students and families flood in, and the holiday weekend right after is one of the busiest of the year. Regulars say the reward for waiting is real - mid-to-late September turns noticeably more relaxed once move-in is done, with thinner crowds and cheaper rooms than either summer or the foliage season that follows. Weather holds up too: early September is still warm enough for the beach, usually less humid than August though posters admit there's no guarantee. The record: 24C days, 15.1C nights, 83mm of rain across 7.3 days, 8.5 hours of sun and a 19.3C sea - good swimming weather if you can dodge the moving trucks.
ボストンのほかの月
Regulars describe the first half of the month as often quite hot and humid, though the intensity typically backs off from July's peak - a pattern regulars are candid doesn't always hold, since some summers bring heat waves that persist well into August regardless. Our row backs the warm, humid read, 28.7C reading as a hot 30C at 73 percent humidity, over 19.1C nights, with 85.5mm of rain across 7.7 days. Regulars planning day trips to Cape Cod, Nantucket or Martha's Vineyard treat this month as prime season for exactly that kind of coastal escape from the city heat. The sea sits at 18.7C. The record: 10.7 hours of sun, a 16.7 kph wind and AQI 52.
May warms faster here than any other month - regulars put the end of it near 72F by day and 55F at night, which is a different city from the one that started the month. Our averages sit in the middle at 20.3C over 10.4C, reading as 19C and 7C in a 19.6 kph wind. It is also among the driest months, 78mm across 9 days, so the waterproof is optional in a way it rarely is here. What is not optional is a layer for the water: the harbour is 13.4C, and whether the day feels like spring or like March depends mostly on which way the wind is coming off it. The record: humidity 73 percent, 9.7 hours of sun inside 14.6 of daylight, and AQI 43.
Regulars will not forecast June here, they give a range: the fifties to the nineties, warm by day with any of hot, humid, rainy or chilly at night. Our row's 26C over 15.7C is the middle of that and not a promise. Their packing list follows from it - plan for the eighties, add a sweater and a waterproof layer, and treat everything as removable. Rain is 79.6mm across 8.8 days. One number worth knowing before booking a boat: the harbour is 16.8C this month, so a morning on the water is a jacket occasion whatever the city is doing, helped along by an 18 kph wind. The record: humidity 73 percent, 11 hours of sun inside 15.2 of daylight, and AQI 51.
Boston forum threads describe January as the coldest and snowiest stretch of the year, with typical highs in the 20s-30s Fahrenheit and real potential for a nor'easter or blizzard - winter precipitation here tends to arrive as snow rather than rain given how cold it stays. Posters were candid that snow totals are genuinely unpredictable from year to year: some Januarys bring almost nothing, others dump a couple of feet with little warning. Wind was flagged repeatedly as a real factor too, with Boston's reputation as a notably windy city compounding the cold and damp. Standard advice across threads: waterproof winter boots, real cold-weather layers, and flexible plans given how quickly conditions can change.
通年のメモはボストンの概要ページにあります。 地図のボストンのカードから自分のメモを追加できます。
ボストンの気候平年値 — 9月
ERA5再解析による月平均値です。AQIはその月の平均US AQI(米国大気質指数)です。
9月のボストンの混雑
その場所自体の混み具合 — 学校休暇や大型連休、編集部がタグ付けした月、そして天気の良さによる人気の高さ。快適スコアには含まれません。
ピークの混雑Student move-in weekend、アメリカ合衆国のSummer break(推定)
ピークの混雑混雑ショルダーシーズン閑散
ボストンの天気が良い月
この旅行先自身の一年間の快適スコアでランキングしています — 混み具合とは別のものです(上の「混雑」を参照)。
天気が最高ボストンの天気が最も良いのは5月、6月、9月です — ひと続きのシーズンではなく、別々の時期です。
9月にはWhales on Stellwagen Bankがあります。
天気が最高天気はまずまず天気が厳しい
9月のボストンのイベント
毎年の季節のイベント、自然の見どころ、休業、祝日 — 厳選し出典を明記しています。
- 自然
Whales on Stellwagen Bank
4月15日〜10月20日 · 例年ホエールシーズンHumpbacks and finbacks feed on the bank an hour out of the harbour from mid-April to late October, and the boats stop for the winter. July and August are the reliable months.
- 季節
Student move-in weekend
8月28日〜9月4日 · 例年学校休暇混雑休業Most student leases turn over on 1 September, known locally as "Allston Christmas": every U-Haul in New England is double-parked in Allston and Brighton, and curbs fill with discarded furniture. Locals plan around it; visitors should too. 出典 ↗
近くで開催中のイベント
ボストンから300 km以内 — 日帰りやちょっとした移動で行けて、今月何かがある場所です。快適スコアには含まれません。
ボストンはどこにある?
9月のボストン — よくある質問
- 9月はボストンを訪れるのに良い時期ですか?
- ボストンの9月:暖かい、雨が多い、空気がきれい — 一年で最も訪れやすい月のひとつ。SeasonMapの快適スコアでは、ボストンの12か月中1位です(90/100)。
- 9月のボストンはどんな天気ですか?
- 9月のボストンは、平均最高気温24°C、最低気温15.1°C、降水量は約82.5 mmで、雨の日はおよそ7.3日です。
- 9月のボストンの大気質はどうですか?
- 9月のボストンの米国大気質指数(US AQI)は、平均約46です。
300 km圏内:KillingtonのFall foliage(9月22日〜10月15日ごろ)、StoweのMount Mansfield summer season(5月25日〜10月15日ごろ)。