United States · 1991–2020

Best time to visit
Chatham.

July leads for comfortable weather in Chatham: typically 24.3°C by day, 17.3°C at night, with 71 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortJuly

Typical high24.3°C

Typical low17.3°C

Rain in July71 mm

Comfort

July

July · August · September

87climate match

Beach

July

July · August · September

66climate match

Outdoors

June

June · September · May

79climate match

The weakest month is January, scoring 5 against July’s 87 — days reach only 3.4°C, 21° 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

53.4° / -3.6°

Feb

53.8° / -3.2°

Mar

56.2° / -0.3°

Apr

2110.6° / 4.3°

May

4915.3° / 8.9°

Jun

7620.5° / 13.7°

Jul

8724.3° / 17.3°

Aug

8624.2° / 17.3°

Sep

7821.1° / 14.8°

Oct

4815.9° / 9.5°

Nov

2411° / 4.5°

Dec

56.6° / 0°

Monthly climate evidence for Chatham — daylight is calculated from latitude, everything else is measured, sea temperature from the nearest open water 10 km away
Month	Day	Night	Rain	Wet days	Sea	Daylight	Comfort	Coverage
January	3.4°C	-3.6°C	103 mm	10.1	5.4°C	9 h 28	5	Strong coverage
February	3.8°C	-3.2°C	97 mm	8.8	4.1°C	10 h 32	5	Strong coverage
March	6.2°C	-0.3°C	112 mm	9.4	4.0°C	11 h 48	5	Strong coverage
April	10.6°C	4.3°C	104 mm	9.3	5.9°C	13 h 16	21	Strong coverage
May	15.3°C	8.9°C	83 mm	8.5	9.5°C	14 h 30	49	Strong coverage
June	20.5°C	13.7°C	81 mm	7.4	14.3°C	15 h 11	76	Strong coverage
July	24.3°C	17.3°C	71 mm	6.1	18.5°C	14 h 55	87	Strong coverage
August	24.2°C	17.3°C	79 mm	6.6	19.6°C	13 h 51	86	Strong coverage
September	21.1°C	14.8°C	94 mm	6.9	17.9°C	12 h 25	78	Strong coverage
October	15.9°C	9.5°C	108 mm	8.6	14.3°C	11 h 01	48	Strong coverage
November	11°C	4.5°C	105 mm	8.1	10.3°C	9 h 46	24	Strong coverage
December	6.6°C	0°C	121 mm	10.4	7.6°C	9 h 10	5	Strong coverage

What has changed

Chatham runs +0.7°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

+0.8

Mar

-0.2

Apr

+0.2

May

+0.3

Jun

+0.5

Jul

+1.1

Aug

+0.9

Sep

+1.0

Oct

+1.4

Nov

+0.4

Dec

+1.4

July daytime highs, 2011–2020. Last recorded: 25.0°C.

Records at CHATHAM, 1972–2021
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	14.4°C5 Jan 1998	-21.1°C16 Jan 2004	80 mm15 Jan 1980	286 mm1998 · driest 40 mm in 2020	47
February	14.4°C25 Feb 2017	-20.0°C14 Feb 2016	89 mm21 Feb 1982	421 mm1982 · driest 31 mm in 1980	49
March	21.1°C28 Mar 1985	-13.9°C1 Mar 1980	66 mm31 Mar 2001	265 mm2001 · driest 19 mm in 2006	47
April	27.2°C18 Apr 2012	-7.2°C7 Apr 1982	67 mm16 Apr 2007	201 mm2007 · driest 30 mm in 2012	45
May	31.1°C26 May 2007	0.6°C8 May 1995	75 mm25 May 1999	180 mm1990 · driest 23 mm in 2015	46
June	32.2°C22 Jun 2012	6.7°C12 Jun 1982	91 mm10 Jun 1977	297 mm2006 · driest 1 mm in 2005	48
July	35.0°C6 Jul 1999	10.6°C6 Jul 1978	97 mm17 Jul 1989	252 mm1986 · driest 13 mm in 2002	47
August	33.9°C2 Aug 1975	8.3°C31 Aug 1976	94 mm19 Aug 2017	198 mm1985 · driest 7 mm in 1993	46
September	29.4°C2 Sep 2010	4.4°C30 Sep 1992	155 mm3 Sep 1972	303 mm1996 · driest 17 mm in 2001	46
October	27.8°C10 Oct 2011	-0.6°C31 Oct 1988	91 mm9 Oct 1982	197 mm2011 · driest 7 mm in 2013	48
November	20.0°C9 Nov 1994	-7.8°C22 Nov 2018	100 mm4 Nov 2007	222 mm2014 · driest 25 mm in 2001	46
December	16.7°C2 Dec 2006	-17.8°C26 Dec 1980	78 mm22 Dec 1975	217 mm1977 · driest 24 mm in 1998	47

Typical days per month at CHATHAM, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	23	4	4
February	0	0	21	3	4
March	0	0	15	4	2
April	0	0	2	3	<1
May	<1	0	0	3	0
June	3	<1	0	3	0
July	14	<1	0	2	0
August	14	<1	0	3	0
September	3	0	0	3	0
October	<1	0	0	3	0
November	0	0	5	3	<1
December	0	0	16	4	2

The best month has moved. On the 1961–1990 numbers the strongest month here was August (scoring 90); on 2011–2025 it is July (89). Both are scored the same way, from the same station — only the climate underneath changed.

How often, not how much — every day in CHATHAM’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	0%	32%	12%	42%	0.7–5.4°C
February	0%	31%	12%	39%	1.5–5.7°C
March	<1%	31%	12%	39%	4.6–7.9°C
April	<1%	31%	11%	37%	9.4–12.0°C
May	10%	28%	9%	32%	14.0–16.4°C
June	48%	26%	9%	27%	19.2–21.5°C
July	78%	20%	8%	15%	22.7–25.5°C
August	77%	21%	8%	18%	22.6–25.2°C
September	51%	24%	10%	24%	19.7–22.1°C
October	8%	28%	11%	32%	14.0–17.0°C
November	<1%	28%	11%	35%	9.5–12.6°C
December	0%	34%	13%	48%	4.1–8.4°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.

1973Each stripe is one year’s mean temperature against the 36-year average. Warmest: 2012. Coolest: 1978.2020

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4932844
NOAA station: USC00191386 · CHATHAM
Station distance: 2.8 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 27 usable years
Daylight: Calculated from latitude 41.68°, mid-month, sunrise to sunset including refraction. Not a station measurement.
Sea temperature: NOAA OISST v2.1 1991–2020 monthly climatology, nearest open water 10 km from the place centre. A sheltered bay can run warmer than the open sea it is measured from.
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 CHATHAM is what differs

Old Harbor→Quitnesset→Shooters Island→

Or put two places side by side: Chatham vs Old Harbor

Best time to visitChatham.

July

July

June

The whole year,without the guesswork.

Chatham runs +0.7°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
Chatham.

The whole year,
without the guesswork.

Chatham runs +0.7°C
on the 1961–1990 baseline.

Nearby, measured,
and named.