United States · 1991–2020

Best time to visit
Williamstown.

September leads for comfortable weather in Williamstown: typically 26°C by day, 13°C at night, with 88 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high26°C

Typical low13°C

Rain in September88 mm

Comfort

September

September · May · June

79climate match

Beach

August

August · July · June

73climate match

Outdoors

October

October · April · May

77climate match

The weakest month is January, scoring 5 against September’s 79 — 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° / -5.2°

Feb

56.3° / -4.2°

Mar

1611.8° / -0.4°

Apr

4918.9° / 4.8°

May

7223.8° / 10.6°

Jun

6827.8° / 15.5°

Jul

5729.7° / 17.9°

Aug

6629.3° / 17°

Sep

7926° / 13°

Oct

5719.2° / 6.4°

Nov

2512.3° / 0.8°

Dec

56.6° / -2.5°

Monthly climate evidence for Williamstown — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	4.3°C	-5.2°C	91 mm	10.7	9 h 40	5	Strong coverage
February	6.3°C	-4.2°C	81 mm	9.5	10 h 39	5	Strong coverage
March	11.8°C	-0.4°C	103 mm	10.5	11 h 49	16	Strong coverage
April	18.9°C	4.8°C	95 mm	10.8	13 h 11	49	Strong coverage
May	23.8°C	10.6°C	116 mm	12.3	14 h 19	72	Strong coverage
June	27.8°C	15.5°C	123 mm	10.1	14 h 56	68	Strong coverage
July	29.7°C	17.9°C	123 mm	10.5	14 h 41	57	Strong coverage
August	29.3°C	17°C	91 mm	8.2	13 h 43	66	Strong coverage
September	26°C	13°C	88 mm	7.5	12 h 24	79	Strong coverage
October	19.2°C	6.4°C	81 mm	8.6	11 h 06	57	Strong coverage
November	12.3°C	0.8°C	76 mm	9.2	9 h 57	25	Strong coverage
December	6.6°C	-2.5°C	94 mm	10.6	9 h 24	5	Strong coverage

What has changed

Williamstown runs +0.1°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

-0.2

Feb

+1.0

Mar

+0.2

Apr

+0.1

May

+0.2

Jun

-0.2

Jul

+0.2

Aug

0.0

Sep

+0.5

Oct

-0.2

Nov

-0.8

Dec

+1.0

September daytime highs, 2011–2025. Last recorded: 27.7°C.

Records at MARIETTA WWTP, 1963–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	25.0°C11 Jan 2020	-30.6°C19 Jan 1994	47 mm3 Jan 2023	167 mm1994 · driest 13 mm in 1981	63
February	25.6°C25 Feb 2017	-23.3°C8 Feb 1977	72 mm19 Feb 2000	193 mm2018 · driest 14 mm in 1968	63
March	30.0°C22 Mar 2026	-18.9°C7 Mar 2015	81 mm4 Mar 1963	260 mm1963 · driest 13 mm in 2003	64
April	32.8°C27 Apr 1990	-7.2°C1 Apr 1964	57 mm2 Apr 2024	181 mm1964 · driest 26 mm in 2010	64
May	33.9°C29 May 1987	-3.3°C10 May 1966	76 mm3 May 2010	237 mm1968 · driest 21 mm in 1964	63
June	37.8°C30 Jun 2012	2.8°C12 Jun 1972	102 mm28 Jun 1998	299 mm1998 · driest 8 mm in 1984	63
July	39.4°C8 Jul 2012	6.7°C1 Jul 1988	75 mm13 Jul 2010	239 mm2013 · driest 35 mm in 1995	64
August	37.8°C17 Aug 1988	3.3°C29 Aug 1986	121 mm5 Aug 1989	271 mm1989 · driest 13 mm in 2002	63
September	36.1°C10 Sep 2002	0.6°C23 Sep 1995	109 mm18 Sep 2004	216 mm2004 · driest 18 mm in 2019	63
October	33.9°C3 Oct 2019	-6.7°C28 Oct 1976	70 mm7 Oct 2019	201 mm2019 · driest 3 mm in 1963	63
November	27.8°C5 Nov 2024	-12.2°C30 Nov 1976	63 mm6 Nov 2017	195 mm1985 · driest 12 mm in 2012	63
December	25.6°C3 Dec 1982	-23.9°C23 Dec 1989	57 mm2 Dec 1991	202 mm1990 · driest 15 mm in 1965	63

Typical days per month at MARIETTA WWTP, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	24	3	4
February	<1	0	22	3	3
March	1	0	18	4	2
April	6	<1	6	3	<1
May	14	4	<1	4	0
June	24	10	0	4	0
July	29	15	0	4	0
August	29	15	0	3	0
September	19	6	0	3	0
October	6	<1	3	3	0
November	<1	0	15	3	<1
December	0	0	22	3	3

How often, not how much — every day in MARIETTA WWTP’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%	34%	9%	46%	0.8–7.9°C
February	2%	33%	9%	42%	2.8–9.8°C
March	12%	33%	11%	44%	9.1–15.6°C
April	31%	36%	10%	47%	16.8–21.0°C
May	53%	37%	12%	48%	21.5–27.2°C
June	67%	32%	13%	39%	26.4–29.8°C
July	68%	32%	12%	37%	28.3–31.4°C
August	73%	27%	11%	31%	27.5–31.0°C
September	70%	25%	9%	25%	24.1–28.1°C
October	39%	27%	8%	28%	17.8–21.6°C
November	10%	31%	9%	39%	9.6–15.3°C
December	1%	33%	9%	43%	2.9–10.2°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.

1964Each stripe is one year’s mean temperature against the 58-year average. Warmest: 2024. Coolest: 1978.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4827351
NOAA station: USC00334927 · MARIETTA WWTP
Station distance: 1.6 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 28 usable years
Daylight: Calculated from latitude 39.40°, 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 MARIETTA WWTP is what differs

Marietta→Devola→Reno→Lower Salem→Alden→Arlington Heights→

Or put two places side by side: Williamstown vs Marietta

Best time to visitWilliamstown.

September

August

October

The whole year,without the guesswork.

Williamstown runs +0.1°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
Williamstown.

The whole year,
without the guesswork.

Williamstown runs +0.1°C
on the 1961–1990 baseline.

Nearby, measured,
and named.