Boston climate

Name: Boston
Address: US

Boston is warmest in July, with average highs of 28 °C, and coldest in January, when nights average -6.5 °C. March is the wettest month (116 mm) and July the driest (74 mm). Figures are 1991–2020 climate normals.

Across a full year Boston averages 1,128 mm of rain, 73 days above 25 °C and 105 days below freezing.

United States · 14 m elevation · population 653,833 · 1991–2020 normals

Temperature below 0 °C to above 30 °C Rain band height is that month’s share of the wettest month

Warmest month July 28 °C
Coldest month January -6.5 °C
Driest month July 74 mm
Wettest month March 116 mm
Least cloud September 52 % cloud
Hottest on record July 40 °C
Coldest on record February -26 °C
Warmest sea August 19 °C

What to expectBoston through the year

Boston has a clear annual cycle: average daily highs run from 1.9 °C in January to 28 °C in July, a swing of 26 °C in mean temperature across the year.

Counted across a normal year, 73 days a year reach 25 °C, 20 of them reach 30 °C, 105 nights drop below freezing. The warmest reading in the 1991–2020 record is 40 °C, in July.

Rain is spread fairly evenly through the year, from 74 mm in July to 116 mm in March. There is no dry season to aim for.

The sea off Boston is warmest in August at 19 °C and coldest in February at 3.3 °C. Sea temperature lags the air by a month or two, which is why late summer swims warmer than early summer at the same air temperature.

Month by month

Month	Avg high	Rainfall	Cloud
January	1.9 °C	93 mm	57 %
February	3.3 °C	83 mm	57 %
March	7.1 °C	116 mm	60 %
April	13.5 °C	101 mm	61 %
May	19.1 °C	80 mm	63 %
June	24.4 °C	88 mm	60 %
July	27.8 °C	74 mm	55 %
August	26.9 °C	86 mm	52 %
September	22.7 °C	90 mm	52 %
October	16.3 °C	108 mm	53 %
November	10.2 °C	94 mm	56 %
December	4.8 °C	116 mm	58 %

Temperature month by month

Month	Avg high	Avg low	Mean	Record high	Record low	Days above 25 °C	Days above 30 °C	Days below 0 °C
January	1.9 °C	-6.5 °C	-2.7 °C	19.8 °C	-26.3 °C	0	0	26
February	3.3 °C	-5.6 °C	-1.7 °C	21.4 °C	-26.5 °C	0	0	24
March	7.1 °C	-1.9 °C	2.1 °C	28.2 °C	-18.2 °C	0	0	20
April	13.5 °C	3.9 °C	8.2 °C	31.6 °C	-10.3 °C	1	0	4
May	19.1 °C	9.7 °C	13.9 °C	34.1 °C	1.1 °C	4	1	0
June	24.4 °C	15.2 °C	19.4 °C	37.4 °C	6.7 °C	14	4	0
July	27.8 °C	18.7 °C	22.9 °C	40.2 °C	11.6 °C	24	8	0
August	26.9 °C	18.1 °C	22.1 °C	36.8 °C	11.3 °C	21	6	0
September	22.7 °C	14.6 °C	18.2 °C	35.8 °C	4.0 °C	8	1	0
October	16.3 °C	8.5 °C	11.9 °C	29.8 °C	-6.6 °C	1	0	0
November	10.2 °C	2.9 °C	6.1 °C	23.2 °C	-12.4 °C	0	0	8
December	4.8 °C	-2.5 °C	0.7 °C	20.2 °C	-18.6 °C	0	0	22

Rain, sun and wind month by month

Month	Rainfall	Wet days	Daylight	Cloud cover	Humidity	Wind	Sea temp
January	93 mm	10	9.4 h/day	57 %	69 %	23 km/h	4.9 °C
February	83 mm	9	11 h/day	57 %	68 %	23 km/h	3.3 °C
March	116 mm	10	12 h/day	60 %	69 %	23 km/h	3.5 °C
April	101 mm	11	13 h/day	61 %	69 %	22 km/h	5.8 °C
May	80 mm	11	15 h/day	63 %	72 %	20 km/h	10.1 °C
June	88 mm	10	15 h/day	60 %	73 %	18 km/h	14.7 °C
July	74 mm	9	15 h/day	55 %	71 %	17 km/h	18.2 °C
August	86 mm	9	14 h/day	52 %	73 %	17 km/h	18.8 °C
September	90 mm	8	13 h/day	52 %	75 %	18 km/h	17.0 °C
October	108 mm	10	11 h/day	53 %	74 %	21 km/h	13.5 °C
November	94 mm	10	9.8 h/day	56 %	73 %	22 km/h	10.2 °C
December	116 mm	10	9.1 h/day	58 %	72 %	23 km/h	7.5 °C

Where Boston ranks

Ranking	Position	Value
Places with the best weather in North America in September	28thof 50	90/100
The coolest places in North America in April	34thof 50	14 °C
The coolest places in North America in March	34thof 50	7.1 °C
The coolest places in North America in May	35thof 50	19 °C
The coolest places in North America in February	39thof 50	3.3 °C
The coolest places in North America year-round	40thof 50	15 °C

Planning a trip? See the best time to visit Boston.

QuestionsCommon questions about Boston’s climate

When is the best time to visit Boston?

That depends on what you want, so the honest answer is a comparison rather than a single month. June, August, September sit closest to 20 °C on average, July is the warmest month and July the driest. The month-by-month table above has the full picture.

How hot does Boston get?

In July, the warmest month, daily highs average 28 °C. About 20 days a year pass 30 °C. The highest value in the 1991–2020 record is 40 °C.

How cold does it get in winter?

Nights average -6.5 °C in January, the coldest month. A normal year has 105 nights below freezing.

Which month is wettest in Boston?

March, averaging 116 mm over 10 days with rain. The driest month is July with 74 mm. The year as a whole averages 1,128 mm.

Are these figures a forecast?

No. They are 1991–2020 climate normals: the average of thirty years, which describes what a month is usually like in Boston rather than what any particular week will bring. Individual years can differ substantially from the normal.

Data sources and method

ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
Open-Meteo — Open-Meteo.com. CC BY 4.0
NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
GeoNames — GeoNames.org. CC BY 4.0

Normal period: 1991–2020
Dataset version: era5-1991-2020-scores1.1
Last processed: 1 August 2026

Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: monthly rankings, daylight hours, beach and comfort scores. Full formulas are on the methodology page.

Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.