United States · 1991–2020

Best time to visit
Cool Valley.

September leads for comfortable weather in Cool Valley: typically 27.2°C by day, 16.3°C at night, with 75 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high27.2°C

Typical low16.3°C

Rain in September75 mm

Comfort

September

September · May · October

79climate match

Beach

August

August · June · July

80climate match

Outdoors

October

October · April · September

85climate match

The weakest month is January, scoring 5 against September’s 79 — days reach only 4.7°C, 19° 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

54.7° / -4.3°

Feb

97.6° / -2.2°

Mar

3113.6° / 2.8°

Apr

5820° / 8.6°

May

7725° / 14.6°

Jun

5629.9° / 19.7°

Jul

4832° / 21.9°

Aug

5531.2° / 20.9°

Sep

7927.2° / 16.3°

Oct

6920.6° / 9.7°

Nov

3213° / 3.2°

Dec

66.9° / -1.8°

Monthly climate evidence for Cool Valley — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	4.7°C	-4.3°C	66 mm	6.7	9 h 44	5	Strong coverage
February	7.6°C	-2.2°C	57 mm	6.4	10 h 41	9	Strong coverage
March	13.6°C	2.8°C	89 mm	8.8	11 h 50	31	Strong coverage
April	20°C	8.6°C	120 mm	9.4	13 h 09	58	Strong coverage
May	25°C	14.6°C	123 mm	10.3	14 h 16	77	Strong coverage
June	29.9°C	19.7°C	114 mm	8	14 h 52	56	Strong coverage
July	32°C	21.9°C	100 mm	7.4	14 h 37	48	Strong coverage
August	31.2°C	20.9°C	86 mm	7.1	13 h 40	55	Strong coverage
September	27.2°C	16.3°C	75 mm	5.5	12 h 23	79	Strong coverage
October	20.6°C	9.7°C	80 mm	7	11 h 07	69	Strong coverage
November	13°C	3.2°C	87 mm	7.1	10 h 01	32	Strong coverage
December	6.9°C	-1.8°C	64 mm	7.1	9 h 28	6	Strong coverage

What has changed

Cool Valley runs +1.6°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

+2.0

Feb

+2.1

Mar

+2.3

Apr

+1.0

May

+1.2

Jun

+1.6

Jul

+0.9

Aug

+0.7

Sep

+1.8

Oct

+1.2

Nov

+1.1

Dec

+3.5

September daytime highs, 2011–2025. Last recorded: 29.4°C.

Records at ST LOUIS LAMBERT INTL AP, 1938–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	25.0°C24 Jan 1950	-27.8°C20 Jan 1985	106 mm3 Jan 1950	229 mm2005 · driest 3 mm in 1986	88
February	30.0°C27 Feb 2024	-24.4°C3 Feb 1996	60 mm5 Feb 2008	133 mm2018 · driest 7 mm in 1963	88
March	33.9°C26 Mar 2026	-20.6°C5 Mar 1960	63 mm18 Mar 2008	213 mm2008 · driest 19 mm in 1941	88
April	33.9°C18 Apr 2002	-5.6°C8 Apr 1972	122 mm11 Apr 1979	276 mm2025 · driest 25 mm in 1977	89
May	36.7°C26 May 1953	-0.6°C10 May 1966	142 mm16 May 1995	328 mm1995 · driest 20 mm in 2005	89
June	42.2°C28 Jun 2012	6.1°C3 Jun 1969	100 mm14 Jun 1957	334 mm2015 · driest 11 mm in 1991	89
July	46.1°C14 Jul 1954	10.6°C6 Jul 1972	220 mm26 Jul 2022	323 mm1948 · driest 13 mm in 1941	89
August	41.7°C29 Aug 1984	8.3°C29 Aug 1986	110 mm3 Aug 2022	375 mm1946 · driest 2 mm in 1971	88
September	40.0°C1 Sep 2011	0.0°C28 Sep 1942	117 mm13 Sep 1945	255 mm1945 · driest 0 mm in 1979	88
October	34.4°C2 Oct 1953	-5.6°C26 Oct 1942	74 mm31 Oct 1946	315 mm2009 · driest 5 mm in 1975	88
November	29.4°C1 Nov 1950	-17.2°C30 Nov 1964	99 mm5 Nov 2024	253 mm1985 · driest 3 mm in 1949	88
December	25.6°C28 Dec 2025	-26.7°C22 Dec 1989	124 mm26 Dec 2015	298 mm2015 · driest 1 mm in 1955	88

Typical days per month at ST LOUIS LAMBERT INTL AP, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	24	2	5
February	<1	0	19	2	4
March	2	<1	10	3	2
April	8	2	1	4	<1
May	17	6	0	4	0
June	27	17	0	4	0
July	30	23	0	3	0
August	30	21	0	3	0
September	21	9	0	2	0
October	8	2	<1	3	0
November	<1	0	9	3	<1
December	0	0	20	2	3

How often, not how much — every day in ST LOUIS LAMBERT INTL AP’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	2%	20%	6%	18%	0.9–7.7°C
February	5%	22%	7%	22%	2.8–10.6°C
March	16%	28%	10%	34%	9.3–16.3°C
April	35%	31%	12%	37%	16.7–22.3°C
May	59%	31%	11%	37%	22.3–27.1°C
June	72%	27%	12%	30%	27.6–31.9°C
July	77%	23%	10%	22%	29.8–33.7°C
August	78%	22%	8%	19%	29.3–33.1°C
September	75%	20%	7%	17%	24.7–29.4°C
October	46%	21%	8%	20%	18.5–23.6°C
November	13%	23%	8%	22%	9.2–15.6°C
December	2%	23%	6%	23%	2.9–9.6°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.

1939Each stripe is one year’s mean temperature against the 87-year average. Warmest: 2024. Coolest: 1978.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4382223
NOAA station: USW00013994 · ST LOUIS LAMBERT INTL AP
Station distance: 6.1 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 30 usable years
Daylight: Calculated from latitude 38.73°, 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 LOUIS LAMBERT INTL AP is what differs

Florissant→Maryland Heights→Hazelwood→Ferguson→Old Jamestown→Overland→

Or put two places side by side: Cool Valley vs Florissant

Best time to visitCool Valley.