セントルイス 9月の天気
セントルイスの9月:暑い、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
セントルイスでは12か月中2位 · 9月に訪れたい旅行先で1413か所中511位 · 快適スコア85/100(Aランク)
- 日中
- 29°C
- 夜
- 15°C
- 雨の日
- 5
- 日照
- 10.2 h
- 湿度
- 67%
- 日の長さ
- 12 h

9月のセントルイスについての旅行者の声
September is the month St Louis regulars pick alongside May, and their framing is that it improves as it runs: the first week or so can still be properly hot, a hangover from a humid July and August, and the comfort builds week by week, with the last third the part they recommend. Mid-September sits in the low 80s Fahrenheit, though they are careful to add that the odd hot day still jumps up out of nowhere. It is fairly dry by local standards too - our row's 83.1mm falls across only 5.3 days, which is thunderstorm rain rather than drizzle - and that combination is why the outdoor events calendar fills up. The record: 28.9C days that feel like 30C, 14.7C nights, humidity 67 percent and 10.2 hours of sun.
セントルイスのほかの月
Regulars describe this month as a genuine toss-up rather than a settled pattern - balmy and pleasant one visit, oppressively humid like the Deep South the next, with the odds of the muggier version rising the closer the calendar gets to July. Our row backs the real heat and building humidity, 31.3C reading as a hot 34C at 66 percent humidity, over 18C nights, with 91.3mm of rain across 6.9 days. Regulars comparing this month to August don't find a clear winner on crowds either, both drawing similar numbers, so the honest deciding factor ends up being which version of the heat gamble a visitor is more willing to take. The record: 12 hours of sun, a 14.7 kph wind and AQI 68.
Regulars call April the most beautiful month here for the blossom and new leaves, and immediately qualify it: this is also when storms and rapid weather swings are most likely, chilly evenings alongside daytime warmth, and their standing advice is to check a local forecast a day or two out rather than trust a seasonal average. Our row shows the range that produces - 19.9C over 6.5C, with 109.5mm of rain across 9.1 days and a trace of snow, 0.5cm, still possible early in the month. Spring and autumn are named as this city's best seasons overall, and April earns that with qualifications rather than without them. The record: humidity 64 percent, 9 hours of sun, a 20.6 kph wind and AQI 42.
Locals put October among the best weeks here and give a date for the end of it: the turn usually does not happen until around Halloween, so the month is autumn in colour and late summer in temperature. Our row reads 21.7C by day against 7.7C at night, a fourteen-degree fall that catches people who packed for the afternoon, and the felt figures are 20C and 6C in a 17.2 kph wind. Rain is light and infrequent, 70.8mm across 5.6 days, and the 0.1cm in the snow column is the first hint of the season rather than a forecast. Early October also beats the fall road-trip crowds further out. The record: humidity 66 percent, 7.8 hours of sun and AQI 36.
Ask the Saint Louis forum for the best time of year and the answer keeps coming back the same: May, then later September into early October, from both a weather and an outdoor-events point of view. The reasoning is what follows it - June through early September is described as quite hot and humid, not New Orleans hot but close, and worth avoiding where you have the choice. May gets the festival calendar without the swelter. The trade-off is water: it is one of the wettest months on the calendar here, though it arrives in bursts rather than all-day grey. The record: 25.6C days, 13.2C nights, 9.8 precipitation days carrying 139.1mm between them, humidity near 70 percent, 10 hours of sun and AQI 53.
通年のメモはセントルイスの概要ページにあります。 地図のセントルイスのカードから自分のメモを追加できます。
セントルイスの気候平年値 — 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月のセントルイスの混雑
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Japanese Festival、Great Forest Park Balloon Race、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
セントルイスの天気が良い月
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)。
天気が最高セントルイスの天気が最も良いのは5月、9月、10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Japanese Festivalがあります。
天気が最高天気はまずまず天気が厳しい
9月のセントルイスのイベント
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。
- ルール
Arch tram timed tickets
1月1日〜12月31日早めの予約をThe ride to the top of the Arch is sold as a timed slot and the summer and holiday-weekend trams go days ahead. The museum underneath is free and needs no ticket at all. 出典 ↗
- 要注意
Summer heat and humidity
6月15日〜9月5日 · 例年酷暑The river valley traps humidity and the heat index runs well above the thermometer for weeks. Forest Park is a morning walk in July, and the Arch grounds have no shade at all. 出典 ↗
- 祭り
Japanese Festival
8月30日〜9月8日 · 例年大きな祭り混雑Three days at the Botanical Garden over Labor Day weekend, running since 1977 and one of the largest of its kind in the country. Evening taiko in the Japanese garden is the reason to go. 出典 ↗
- 祭り
Great Forest Park Balloon Race
9月14日〜22日 · 例年スポーツイベント混雑A Friday-night balloon glow and a Saturday race from Forest Park, free, with seventy balloons and a six-figure crowd on the grass. The most-attended single-day balloon event in America. 出典 ↗
セントルイスはどこにある?
9月のセントルイス — よくある質問
- 9月はセントルイスを訪れるのに良い時期ですか?
- セントルイスの9月:暑い、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、セントルイスの12か月中2位です(85/100)。
- 9月のセントルイスはどんな天気ですか?
- 9月のセントルイスは、平均最高気温28.9°C、最低気温14.7°C、降水量は約83.1 mmで、雨の日はおよそ5.3日です。
- 9月のセントルイスの大気質はどうですか?
- 9月のセントルイスの米国大気質指数(US AQI)は、平均約50です。