United States · 1991–2020

Best time to visit
Waterloo.

September leads for comfortable weather in Waterloo: typically 27°C by day, 13.9°C at night, with 87 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high27°C

Typical low13.9°C

Rain in September87 mm

Comfort

September

September · May · October

78climate match

Beach

July

July · August · June

74climate match

Outdoors

October

October · April · May

82climate match

The weakest month is January, scoring 5 against September’s 78 — days reach only 5.2°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

55.2° / -5.3°

Feb

88.1° / -3.6°

Mar

2513.4° / 1°

Apr

5319.9° / 6.6°

May

7524.6° / 12.2°

Jun

6229.3° / 17.1°

Jul

5631.1° / 19.5°

Aug

6130.6° / 18.4°

Sep

7827° / 13.9°

Oct

6821° / 7.5°

Nov

2913.3° / 1.6°

Dec

57.2° / -3.1°

Monthly climate evidence for Waterloo — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	5.2°C	-5.3°C	70 mm	6.2	9 h 46	5	Strong coverage
February	8.1°C	-3.6°C	63 mm	5.8	10 h 42	8	Strong coverage
March	13.4°C	1°C	102 mm	9.3	11 h 50	25	Strong coverage
April	19.9°C	6.6°C	126 mm	9.1	13 h 08	53	Strong coverage
May	24.6°C	12.2°C	117 mm	9.8	14 h 14	75	Strong coverage
June	29.3°C	17.1°C	122 mm	8.3	14 h 49	62	Strong coverage
July	31.1°C	19.5°C	97 mm	7.4	14 h 35	56	Strong coverage
August	30.6°C	18.4°C	94 mm	6.3	13 h 39	61	Strong coverage
September	27°C	13.9°C	87 mm	5.8	12 h 23	78	Strong coverage
October	21°C	7.5°C	73 mm	6.3	11 h 08	68	Strong coverage
November	13.3°C	1.6°C	92 mm	7.3	10 h 02	29	Strong coverage
December	7.2°C	-3.1°C	72 mm	6.5	9 h 30	5	Strong coverage

What has changed

Waterloo runs +0.0°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

+0.8

Feb

+0.4

Mar

-0.3

Apr

-0.5

May

-0.2

Jun

+0.1

Jul

-0.4

Aug

-0.9

Sep

+0.7

Oct

-0.5

Nov

-0.8

Dec

+1.9

September daytime highs, 2011–2023. Last recorded: 28.7°C.

Records at FESTUS, 1960–2024
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	25.6°C28 Jan 1970	-32.8°C17 Jan 1977	80 mm29 Jan 1969	162 mm2005 · driest 3 mm in 1970	56
February	31.7°C13 Feb 1962	-28.9°C10 Feb 1982	65 mm22 Feb 1975	207 mm2018 · driest 7 mm in 2017	53
March	32.8°C28 Mar 1985	-25.0°C5 Mar 1978	97 mm19 Mar 2008	248 mm2008 · driest 38 mm in 1966	57
April	33.9°C23 Apr 1965	-7.8°C11 Apr 1973	106 mm19 Apr 2013	334 mm1994 · driest 13 mm in 1980	55
May	35.6°C15 May 2013	-2.8°C1 May 1963	86 mm28 May 1964	266 mm1995 · driest 9 mm in 1978	55
June	42.2°C30 Jun 2012	2.8°C1 Jun 1966	109 mm16 Jun 2000	354 mm1997 · driest 4 mm in 1971	56
July	43.3°C15 Jul 1980	6.1°C6 Jul 1972	83 mm28 Jul 1979	227 mm1998 · driest 2 mm in 1974	57
August	41.1°C21 Aug 1962	4.4°C28 Aug 1967	151 mm15 Aug 2016	258 mm2016 · driest 12 mm in 1983	56
September	40.6°C14 Sep 1971	-1.1°C23 Sep 1983	158 mm8 Sep 2018	274 mm1993 · driest 0 mm in 1979	57
October	36.1°C8 Oct 1980	-7.8°C16 Oct 1976	104 mm20 Oct 2016	286 mm2009 · driest 3 mm in 1963	57
November	30.6°C7 Nov 1980	-16.7°C30 Nov 1976	90 mm22 Nov 1963	248 mm1972 · driest 8 mm in 1999	55
December	26.1°C4 Dec 2021	-28.3°C23 Dec 1989	94 mm10 Dec 1971	205 mm1967 · driest 4 mm in 1976	53

Typical days per month at FESTUS, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	25	2	2
February	<1	0	21	2	2
March	2	<1	14	3	<1
April	7	1	4	4	0
May	17	5	0	4	0
June	27	15	0	4	0
July	30	20	0	3	0
August	29	18	0	3	0
September	21	9	0	3	0
October	9	1	3	3	0
November	<1	0	13	3	<1
December	0	0	22	2	1

The best month has moved. On the 1961–1990 numbers the strongest month here was May (scoring 77); on 2011–2025 it is September (81). Both are scored the same way, from the same station — only the climate underneath changed.

How often, not how much — every day in FESTUS’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%	19%	7%	15%	1.3–8.6°C
February	7%	19%	8%	18%	3.6–11.5°C
March	18%	28%	12%	31%	10.6–17.5°C
April	39%	30%	14%	36%	17.8–23.1°C
May	62%	29%	12%	35%	22.6–27.6°C
June	76%	24%	10%	26%	27.8–31.1°C
July	78%	22%	10%	20%	29.8–33.9°C
August	80%	20%	9%	18%	29.0–32.6°C
September	77%	20%	9%	15%	24.6–29.9°C
October	53%	18%	8%	19%	19.5–23.2°C
November	18%	22%	9%	20%	9.8–16.6°C
December	3%	21%	8%	21%	4.5–11.1°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.

1961Each stripe is one year’s mean temperature against the 44-year average. Warmest: 2012. Coolest: 1993.2023

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4252548
NOAA station: USC00232850 · FESTUS
Station distance: 24.5 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 26 usable years
Daylight: Calculated from latitude 38.34°, 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 FESTUS is what differs

Festus→De Soto→Barnhart→Pevely→Crystal City→Imperial→

Or put two places side by side: Waterloo vs Festus

Best time to visitWaterloo.