United States · 1991–2020

Best time to visit
Merrimac.

September leads for comfortable weather in Merrimac: typically 25.5°C by day, 12.7°C at night, with 114 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high25.5°C

Typical low12.7°C

Rain in September114 mm

Comfort

September

September · May · June

77climate match

Beach

August

August · July · June

71climate match

Outdoors

October

October · April · May

78climate match

The weakest month is January, scoring 5 against September’s 77 — days reach only 6.4°C, 18° below the 24°C the score treats as ideal, and nights drop to -5.3°C.

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

56.4° / -5.3°

Feb

67.9° / -4.7°

Mar

2713.2° / -0.5°

Apr

5419.5° / 4.9°

May

7323.8° / 10°

Jun

6828.1° / 15.3°

Jul

6029.9° / 17.4°

Aug

6629.1° / 16.8°

Sep

7725.5° / 12.7°

Oct

5819.4° / 5.9°

Nov

3614.3° / 0.6°

Dec

68.5° / -3.3°

Monthly climate evidence for Merrimac — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	6.4°C	-5.3°C	61 mm	5.5	9 h 45	5	Good coverage
February	7.9°C	-4.7°C	62 mm	5	10 h 42	6	Good coverage
March	13.2°C	-0.5°C	83 mm	6.4	11 h 50	27	Good coverage
April	19.5°C	4.9°C	95 mm	8.3	13 h 09	54	Good coverage
May	23.8°C	10°C	117 mm	9.5	14 h 14	73	Good coverage
June	28.1°C	15.3°C	122 mm	8.9	14 h 50	68	Good coverage
July	29.9°C	17.4°C	119 mm	7.8	14 h 36	60	Good coverage
August	29.1°C	16.8°C	98 mm	8.2	13 h 39	66	Good coverage
September	25.5°C	12.7°C	114 mm	6.3	12 h 23	77	Good coverage
October	19.4°C	5.9°C	94 mm	5.9	11 h 08	58	Good coverage
November	14.3°C	0.6°C	67 mm	5.2	10 h 02	36	Good coverage
December	8.5°C	-3.3°C	85 mm	5.9	9 h 30	6	Good coverage

Records at BOSTON 4 SE, 1998–2015
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	27.2°C31 Jan 2002	-24.4°C7 Jan 2014	71 mm14 Jan 2005	136 mm1999 · driest 15 mm in 2015	17
February	26.7°C26 Feb 2000	-17.2°C7 Feb 2007	77 mm8 Feb 2013	168 mm2003 · driest 7 mm in 2009	16
March	29.4°C9 Mar 2000	-18.9°C4 Mar 2014	54 mm7 Mar 2011	146 mm2013 · driest 0 mm in 2006	17
April	34.4°C26 Apr 2009	-5.6°C9 Apr 2007	61 mm20 Apr 2015	191 mm2011 · driest 25 mm in 2010	17
May	35.0°C14 May 2000	-1.7°C22 May 2002	85 mm16 May 2014	189 mm2009 · driest 38 mm in 2007	17
June	37.8°C13 Jun 2002	6.1°C2 Jun 2003	91 mm10 Jun 2013	194 mm2000 · driest 37 mm in 2011	17
July	37.8°C10 Jul 2007	8.9°C12 Jul 2002	103 mm8 Jul 2005	179 mm2003 · driest 24 mm in 2011	17
August	38.3°C9 Aug 2007	9.4°C7 Aug 2004	67 mm16 Aug 2012	151 mm2013 · driest 43 mm in 2006	16
September	36.1°C8 Sep 1998	2.8°C30 Sep 2003	107 mm2 Sep 2006	302 mm1999 · driest 4 mm in 2014	16
October	32.8°C10 Oct 2007	-5.6°C21 Oct 2014	90 mm8 Oct 2005	193 mm2005 · driest 2 mm in 2000	17
November	27.8°C6 Nov 2003	-14.4°C30 Nov 2013	44 mm8 Nov 2006	162 mm2006 · driest 0 mm in 2012	17
December	26.7°C8 Dec 1998	-15.0°C23 Dec 2000	63 mm17 Dec 2000	145 mm2009 · driest 37 mm in 2001	17

Typical days per month at BOSTON 4 SE, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	<1	0	26	2	2
February	<1	0	24	2	2
March	1	0	19	3	<1
April	7	1	4	3	<1
May	14	3	<1	4	0
June	24	11	0	4	0
July	27	15	0	3	0
August	26	12	0	3	0
September	17	4	0	3	0
October	4	<1	4	3	0
November	<1	0	16	2	0
December	<1	0	24	3	<1

How often, not how much — every day in BOSTON 4 SE’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	3%	18%	7%	13%	3.6–9.3°C
February	3%	18%	7%	10%	3.6–11.2°C
March	16%	21%	9%	17%	10.0–15.5°C
April	38%	28%	10%	31%	18.1–20.7°C
May	58%	31%	13%	34%	21.7–25.7°C
June	70%	30%	14%	31%	26.7–29.6°C
July	74%	25%	12%	28%	28.4–31.7°C
August	73%	26%	11%	28%	27.1–30.6°C
September	74%	21%	10%	17%	23.9–28.0°C
October	43%	19%	10%	20%	18.0–21.0°C
November	14%	18%	8%	12%	11.9–16.7°C
December	4%	19%	9%	14%	5.2–11.6°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.

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4772739
NOAA station: USC00440860 · BOSTON 4 SE
Station distance: 10.5 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 16 usable years
Daylight: Calculated from latitude 38.45°, 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 BOSTON 4 SE is what differs

Culpeper→Round Hill→Alanthus→Amissville→Batna→Belle Parc→

Or put two places side by side: Merrimac vs Culpeper

Best time to visitMerrimac.