United States · 1991–2020

Best time to visit
Ballwin.

September leads for comfortable weather in Ballwin: typically 26.9°C by day, 14.1°C at night, with 85 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high26.9°C

Typical low14.1°C

Rain in September85 mm

Comfort

September

September · May · October

80climate match

Beach

August

August · July · June

77climate match

Outdoors

October

October · April · September

80climate match

The weakest month is January, scoring 5 against September’s 80 — days reach only 4.3°C, 20° below the 24°C the score treats as ideal.

Month by month

The whole year,
without the guesswork.

The bars show the comfort score. Day and night temperatures come from daily observed highs and lows; rain is the historical monthly estimate.

Jan

54.3° / -6.2°

Feb

57.2° / -4.3°

Mar

2512.8° / 0.9°

Apr

5419.3° / 6.9°

May

7524.4° / 12.8°

Jun

6329.2° / 17.9°

Jul

5431.4° / 20.1°

Aug

6130.7° / 18.9°

Sep

8026.9° / 14.1°

Oct

6420.5° / 7.5°

Nov

2913.1° / 1.5°

Dec

56.9° / -3.5°

Monthly climate evidence for Ballwin — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	4.3°C	-6.2°C	62 mm	5.4	9 h 45	5	Strong coverage
February	7.2°C	-4.3°C	61 mm	6	10 h 41	5	Strong coverage
March	12.8°C	0.9°C	90 mm	8.9	11 h 50	25	Strong coverage
April	19.3°C	6.9°C	113 mm	8.9	13 h 09	54	Strong coverage
May	24.4°C	12.8°C	129 mm	10.1	14 h 15	75	Strong coverage
June	29.2°C	17.9°C	107 mm	7.9	14 h 51	63	Strong coverage
July	31.4°C	20.1°C	100 mm	6.9	14 h 37	54	Strong coverage
August	30.7°C	18.9°C	84 mm	6.2	13 h 40	61	Strong coverage
September	26.9°C	14.1°C	85 mm	5.4	12 h 23	80	Strong coverage
October	20.5°C	7.5°C	87 mm	7.4	11 h 07	64	Strong coverage
November	13.1°C	1.5°C	87 mm	7.1	10 h 01	29	Strong coverage
December	6.9°C	-3.5°C	67 mm	6.5	9 h 29	5	Strong coverage

What has changed

Ballwin runs +0.8°C
on the 1961–1990 baseline.

Each bar compares the 2011–2025 daytime average for that month against the same month in 1961–1990, measured at the same station. Months where the older record is too thin to compare are left blank.

Jan

+0.9

Feb

+1.1

Mar

+1.4

Apr

+0.1

May

+0.1

Jun

+0.4

Jul

—

Aug

-0.3

Sep

+0.7

Oct

+1.1

Nov

—

Dec

+3.0

September daytime highs, 2011–2025. Last recorded: 29.1°C.

Records at ST CHARLES 7 SSW, 1975–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	23.9°C22 Jan 1986	-27.8°C21 Jan 1985	102 mm10 Jan 1975	243 mm2005 · driest 0 mm in 2000	52
February	28.9°C28 Feb 2024	-27.8°C3 Feb 1996	89 mm2 Feb 1986	148 mm1986 · driest 7 mm in 2024	52
March	33.9°C27 Mar 2026	-22.2°C5 Mar 1978	63 mm19 Mar 2008	156 mm2018 · driest 25 mm in 1986	52
April	33.3°C19 Apr 2002	-6.7°C8 Apr 1990	99 mm30 Apr 2017	261 mm2025 · driest 15 mm in 1988	51
May	36.7°C27 May 2012	-1.1°C7 May 1992	97 mm7 May 2000	301 mm2004 · driest 17 mm in 1979	52
June	40.6°C29 Jun 2012	5.0°C5 Jun 1993	84 mm12 Jun 2002	318 mm2015 · driest 7 mm in 1991	52
July	41.1°C16 Jul 1980	10.0°C10 Jul 1996	182 mm26 Jul 2022	306 mm2022 · driest 20 mm in 1997	50
August	41.1°C30 Aug 1984	6.1°C16 Aug 1992	102 mm9 Aug 2020	196 mm2019 · driest 0 mm in 2013	50
September	38.3°C2 Sep 1984	-1.7°C23 Sep 1995	83 mm23 Sep 1993	255 mm1993 · driest 2 mm in 1979	51
October	34.4°C4 Oct 2006	-5.6°C11 Oct 1993	79 mm20 Oct 2016	343 mm2009 · driest 0 mm in 1988	49
November	29.4°C2 Nov 2016	-18.9°C8 Nov 1991	148 mm5 Nov 2024	246 mm2024 · driest 0 mm in 1999	50
December	25.0°C29 Dec 2025	-28.9°C23 Dec 1989	135 mm27 Dec 2015	236 mm2015 · driest 5 mm in 1980	51

Typical days per month at ST CHARLES 7 SSW, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	26	2	1
February	<1	0	22	2	1
March	2	0	14	3	<1
April	6	1	3	4	0
May	15	5	<1	4	0
June	25	14	0	3	0
July	29	21	0	3	0
August	28	18	0	3	0
September	20	8	<1	3	0
October	8	2	3	3	0
November	<1	0	12	3	<1
December	0	0	23	2	1

How often, not how much — every day in ST CHARLES 7 SSW’s record sorted by what it was actually like, rather than averaged
Month	Warm & dry days	Wet days	Washouts	Week with 3+ wet days	Daytime mean has ranged
January	1%	17%	5%	14%	0.6–7.6°C
February	6%	20%	7%	18%	2.0–10.7°C
March	15%	29%	10%	35%	9.7–16.4°C
April	35%	29%	13%	36%	16.6–22.2°C
May	58%	32%	13%	38%	22.3–26.8°C
June	73%	26%	11%	28%	27.5–31.1°C
July	77%	23%	11%	22%	29.9–33.6°C
August	79%	21%	9%	19%	28.9–33.1°C
September	76%	18%	9%	13%	24.9–28.9°C
October	44%	22%	9%	25%	18.6–22.7°C
November	15%	24%	11%	24%	9.8–16.6°C
December	3%	21%	7%	20%	3.3–9.8°C

A warm and dry day reaches 20°C with under 1 mm of rain; a wet day gets 1 mm or more; a washout gets 10 mm or more. The week column is the share of seven-day stretches in that month, across the station’s whole daily record, that contained three or more wet days — the odds a week-long trip is rained on repeatedly, counted rather than modelled. The last column is the 10th to 90th percentile of that month’s daytime average across individual years: a narrow band means the average is what you will get, a wide one means the average is a midpoint between years that felt quite different.

1976Each stripe is one year’s mean temperature against the 41-year average. Warmest: 2024. Coolest: 1996.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4375663
NOAA station: USC00237398 · ST CHARLES 7 SSW
Station distance: 10.2 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 27 usable years
Daylight: Calculated from latitude 38.60°, mid-month, sunrise to sunset including refraction. Not a station measurement.
Important limit: Historical climate is not a forecast. Nearby stations can miss mountains, coasts, and local microclimates.

These places read the same station, so their numbers are identical — distance from ST CHARLES 7 SSW is what differs

Chesterfield→Creve Coeur→Manchester→Town and Country→Murphy→Des Peres→

Or put two places side by side: Ballwin vs Chesterfield

Best time to visitBallwin.