United States · 1991–2020

Best time to visit
Old Greenwich.

September leads for comfortable weather in Old Greenwich: typically 24.8°C by day, 12.9°C at night, with 123 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high24.8°C

Typical low12.9°C

Rain in September123 mm

Comfort

September

September · June · May

77climate match

Beach

July

July · August · June

72climate match

Outdoors

October

October · May · April

71climate match

The weakest month is January, scoring 5 against September’s 77 — days reach only 3.8°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

53.8° / -6.1°

Feb

55.5° / -5.7°

Mar

610° / -1.5°

Apr

4017.1° / 3.8°

May

7022.8° / 9.3°

Jun

7127.2° / 14.1°

Jul

6529.8° / 17.3°

Aug

6928.8° / 16.6°

Sep

7724.8° / 12.9°

Oct

5218.6° / 6.6°

Nov

2212.3° / 1.1°

Dec

56.6° / -2.9°

Monthly climate evidence for Old Greenwich — daylight is calculated from latitude, everything else is measured, sea temperature from the nearest open water 20 km away
Month	Day	Night	Rain	Wet days	Sea	Daylight	Comfort	Coverage
January	3.8°C	-6.1°C	104 mm	9	3.8°C	9 h 31	5	Good coverage
February	5.5°C	-5.7°C	80 mm	7.2	1.9°C	10 h 34	5	Good coverage
March	10°C	-1.5°C	126 mm	8.7	2.8°C	11 h 49	6	Good coverage
April	17.1°C	3.8°C	111 mm	10	6.8°C	13 h 15	40	Good coverage
May	22.8°C	9.3°C	102 mm	10	12.5°C	14 h 27	70	Good coverage
June	27.2°C	14.1°C	118 mm	8.6	18.3°C	15 h 06	71	Good coverage
July	29.8°C	17.3°C	91 mm	7.8	22.2°C	14 h 51	65	Good coverage
August	28.8°C	16.6°C	94 mm	7.9	23.1°C	13 h 48	69	Good coverage
September	24.8°C	12.9°C	123 mm	7.7	21.8°C	12 h 25	77	Good coverage
October	18.6°C	6.6°C	112 mm	7.4	18.0°C	11 h 02	52	Good coverage
November	12.3°C	1.1°C	108 mm	7.8	12.7°C	9 h 50	22	Good coverage
December	6.6°C	-2.9°C	108 mm	9.3	7.8°C	9 h 14	5	Good coverage

What has changed

Old Greenwich runs +0.5°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

+0.5

Feb

+0.4

Mar

-0.2

Apr

0.0

May

+0.4

Jun

+0.1

Jul

+0.6

Aug

+0.6

Sep

+1.1

Oct

+0.5

Nov

+0.1

Dec

+1.6

September daytime highs, 2013–2021. Last recorded: 25.0°C.

Records at STAMFORD 5 N, 1955–2022
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	20.6°C6 Jan 2007	-27.8°C18 Jan 1982	105 mm21 Jan 1979	293 mm1979 · driest 17 mm in 1981	58
February	23.3°C24 Feb 1985	-26.1°C5 Feb 1996	72 mm20 Feb 1981	177 mm1981 · driest 18 mm in 1987	60
March	29.4°C31 Mar 1998	-21.1°C19 Mar 1967	97 mm14 Mar 2010	300 mm2010 · driest 8 mm in 2021	59
April	35.6°C17 Apr 2002	-8.9°C1 Apr 1964	104 mm15 Apr 2007	323 mm1983 · driest 27 mm in 1985	61
May	36.1°C20 May 1996	-2.2°C3 May 1957	115 mm29 May 1968	351 mm1989 · driest 3 mm in 2020	59
June	36.1°C16 Jun 1957	1.7°C3 Jun 1986	155 mm19 Jun 1972	413 mm1972 · driest 0 mm in 2020	60
July	38.9°C15 Jul 1995	6.1°C6 Jul 1979	103 mm13 Jul 1996	222 mm1984 · driest 19 mm in 2020	60
August	40.0°C9 Aug 2001	2.8°C31 Aug 1965	92 mm19 Aug 1991	214 mm1991 · driest 11 mm in 1995	60
September	36.1°C11 Sep 1983	-2.2°C28 Sep 1957	128 mm16 Sep 1999	329 mm1999 · driest 0 mm in 2017	58
October	32.8°C2 Oct 2019	-8.9°C28 Oct 1976	106 mm7 Oct 1972	374 mm2005 · driest 6 mm in 1963	61
November	27.8°C3 Nov 2003	-13.9°C24 Nov 1989	85 mm8 Nov 1977	238 mm1988 · driest 0 mm in 2016	61
December	24.4°C7 Dec 1998	-25.0°C26 Dec 1980	77 mm3 Dec 1986	235 mm1983 · driest 15 mm in 1980	62

Typical days per month at STAMFORD 5 N, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	26	3	5
February	0	0	25	3	4
March	<1	0	20	4	3
April	3	<1	6	4	<1
May	10	3	<1	3	0
June	22	8	0	4	0
July	29	16	0	3	0
August	28	12	0	3	0
September	16	3	0	4	0
October	3	0	3	3	0
November	<1	0	14	3	<1
December	0	0	23	4	3

How often, not how much — every day in STAMFORD 5 N’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%	28%	10%	31%	0.6–6.2°C
February	<1%	26%	10%	27%	2.0–8.2°C
March	4%	28%	11%	34%	7.3–12.1°C
April	22%	31%	12%	39%	14.7–18.6°C
May	54%	30%	11%	39%	20.1–24.6°C
June	70%	28%	11%	31%	25.3–28.4°C
July	74%	26%	10%	27%	27.7–31.0°C
August	74%	26%	10%	26%	27.0–30.2°C
September	68%	25%	11%	28%	23.0–26.1°C
October	32%	22%	10%	20%	16.9–20.1°C
November	5%	28%	12%	31%	9.9–14.3°C
December	<1%	29%	11%	35%	2.8–8.6°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.

1956Each stripe is one year’s mean temperature against the 52-year average. Warmest: 1998. Coolest: 1958.2019

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4839983
NOAA station: USC00067970 · STAMFORD 5 N
Station distance: 11.4 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 19 usable years
Daylight: Calculated from latitude 41.02°, mid-month, sunrise to sunset including refraction. Not a station measurement.
Sea temperature: NOAA OISST v2.1 1991–2020 monthly climatology, nearest open water 20 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 STAMFORD 5 N is what differs

Stamford→North Stamford→Norwalk→East Norwalk→Westport→Darien→

Or put two places side by side: Old Greenwich vs Stamford

Best time to visitOld Greenwich.