Brookline weather in September

In September, Brookline sees average daytime highs of 71°F and overnight lows near 58°F, with 3.5 in of rain across 8.2 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 7th-wettest month of the year here.

Highs ease over the month, from about 75°F in the first days to 67°F by the end. The sky is clear or mostly clear about 39% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Brookline's 1st-clearest and 9th-windiest month. For the whole year in context, see Brookline's year-round climate.

Daytime high
71°
4th warmest
Overnight low
58°
9th coldest
Rainfall
3.5 in
8.2 wet days
Daylight
12 h 18 min
5:30 AM – 5:47 PM
Cloud cover
54%
1st clearest
Wind
8 mph
9th windiest
Solar energy
4.16 kWh/m²
Travel score
6.9
out of 10

Brookline is town in Massachusetts, United States.

Founded
1638

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 75°F in the first days to 67°F by the end.

A typical September day in Brookline reaches about 71°F in the afternoon and slips back to 58°F overnight — a 13°F spread between the day's warmth and the night's chill. On most days the high lands between 63°F and 80°F. Set against its neighbours, September runs about 7°F cooler than August and about 10°F warmer than October.

40°50°60°70°80°151015202530
Avg high (°F)Avg low (°F)
17562
27562
37562
47461
57461
67461
77460
87360
97360
107360
117359
127259
137259
147258
157158
167158
177157
187157
197057
207056
216956
226956
236956
246955
256855
266855
276754
286754
296754
306653

How September really feels in Brookline

Once humidity and wind are folded in, September averages 0 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
0
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Brookline weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan36° / 24°3.7105.69.30.0
Feb38° / 25°3.38.85.110.30.0
Mar44° / 31°4.611.14.611.60.8
Apr54° / 41°3.911113.13.2
May64° / 50°3.210.6014.45.5
Jun73° / 59°3.410.10156.6
Jul79° / 65°2.99.6014.86.7
Aug78° / 65°3.49.2013.77.0
Sep71° / 58°3.58.2012.36.9
Oct61° / 48°4.39.80.110.85.1
Nov50° / 38°3.79.60.89.62.4
Dec41° / 30°4.510.84.390.3

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 39% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 13% of September, with mostly cloudy or overcast conditions the remaining 47%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15644
25545
35545
45446
55446
65446
75446
85446
95347
105347
115347
125347
135347
145446
155446
165347
175347
185248
195248
205248
215149
225149
235149
245149
255149
265149
275248
285248
295248
305248

Chance of precipitation in September

Any precipitation

Brookline gets around 3.5 in of rain over 8.2 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 27% and peaks near 30% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
125
225
326
426
526
626
727
827
927
1027
1127
1227
1327
1427
1527
1627
1726
1826
1926
2027
2127
2227
2327
2427
2528
2628
2729
2829
2929
3030

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the dry band about 43% of days. Sticky, muggy-or-worse air turns up on roughly 13% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1232926184
2242926184
3252925174
4262924173
5282924163
6292823163
7312823163
8332822152
9342722152
10352622152
11372621142
12382521141
13402521131
14412520131
15432520121
16442419121
17452419110
18462419110
19472418100
20492418100
2150241790
2251241690
2352241680
2453241580
2555241470
2657231370
2758231360
2859231260
2962221150
3063211150

Wind in September

Winds average 8 mph in September.

Across September, daily wind ranges from about 8 mph on the calmest days to 9 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
18light breeze
28light breeze
38light breeze
48light breeze
58light breeze
68light breeze
78light breeze
88light breeze
98light breeze
108light breeze
118light breeze
128light breeze
138light breeze
148light breeze
158light breeze
168light breeze
178light breeze
188light breeze
198light breeze
208light breeze
218light breeze
228light breeze
238light breeze
248light breeze
258light breeze
268light breeze
278light breeze
288light breeze
298light breeze
309light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 hours at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 84 minutes over September. Sunrise moves from 5:14 AM to 5:46 AM, and sunset from 6:14 PM to 5:22 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:146:14
213.05:156:13
312.95:166:11
412.95:176:09
512.85:186:07
612.85:196:05
712.75:216:04
812.75:226:02
912.65:236:00
1012.65:245:58
1112.55:255:56
1212.55:265:55
1312.45:275:53
1412.45:285:51
1512.35:295:49
1612.35:305:47
1712.25:315:45
1812.25:335:44
1912.15:345:42
2012.15:355:40
2112.05:365:38
2212.05:375:36
2311.95:385:34
2411.95:395:33
2511.85:405:31
2611.85:415:29
2711.75:435:27
2811.75:445:25
2911.65:455:23
3011.65:465:22

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.16 kWh/m².

For context, solar energy here swings from a low near 1.6 kWh/m² to a high of 5.95 kWh/m² in July across the year — September's 4.16 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.8Bright
34.7Bright
44.7Bright
54.6Bright
64.6Bright
74.5Bright
84.5Bright
94.4Bright
104.4Bright
114.3Bright
124.3Bright
134.3Bright
144.2Bright
154.2Bright
164.2Bright
174.1Bright
184.1Bright
194.0Bright
204.0Moderate
214.0Moderate
223.9Moderate
233.9Moderate
243.8Moderate
253.8Moderate
263.7Moderate
273.7Moderate
283.6Moderate
293.6Moderate
303.5Moderate
Planning a trip in September

Hazard calendar for Brookline

In seasonPeak

In September, Brookline sits inside its atlantic hurricane season. The full year is below, with each hazard's peak months called out.

Brookline sits in the Atlantic hurricane belt; the season peaks August–October.

Atlantic hurricane
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Brookline?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

6.9
Sightseeing
2nd-best month of the year
4.7
Beach & pool
4th-best month of the year

September is a reasonable time to visit Brookline for sightseeing.

What to pack for Brookline in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Brookline sees daytime highs around 71°F and nights near 58°F. Worth packing: rain gear. About 8 days see rain.

rain gear

Sea temperature near Brookline in September

The nearest coast averages about 63°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 13 mi away) is warmest in August at about 66°F and coldest in February near 38°F.

The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.

40°50°60°70°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshing
Sea temperature (°F)Comfort
Jan41Bracing
Feb38Bracing
Mar38Bracing
Apr42Bracing
May50Bracing
Jun58Bracing
Jul65Cool
Aug66Cool
Sep63Cool
Oct56Bracing
Nov50Bracing
Dec46Bracing

UV index in Brookline in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Brookline peaks around July 10 at about 7 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near January 1 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighHighModerateLowJul 10UV 7Jan 1UV 1
UV index (midday)Level
Jan1Low
Feb3Moderate
Mar4Moderate
Apr5High
May7Very high
Jun7Very high
Jul7Very high
Aug5Moderate
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low

Air quality in Brookline in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Brookline is worst in July — around 16 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (November, 8 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1516 µg/m³Nov 189 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb13Moderate
Mar14Moderate
Apr14Moderate
May15Moderate
Jun15Moderate
Jul16Moderate
Aug14Moderate
Sep12Good
Oct10Good
Nov8Good
Dec10Good
Location & terrain

Where is Brookline?

Brookline sits at 42.3°N, 71.1°W, 33 ft above sea level, in United States. The nearest listed city is Mission Hill, 0.6 mi away.

Topography around Brookline

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Brookline.

Within 2 miles, the terrain around Brookline has only modest variations in elevation — a maximum elevation change of 358 ft around an average of 105 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 633 ft; within 50 miles, large variations in elevation — a maximum elevation change of 2,185 ft.

The land around Brookline is covered by artificial surfaces (48%) and trees (43%) within 2 miles, trees (50%) and artificial surfaces (28%) within 10 miles, and trees (63%) and water (28%) within 50 miles.

2 miles
358 ft
10 miles
633 ft
50 miles
2,185 ft
treesgrasslandartificial surfaceswaterwetland
September weather nearby: Mission Hill 0.6 mi · Fenway/Kenmore 1.2 mi · Jamaica Plain 1.2 mi · Roxbury Crossing 1.2 mi · Allston 1.9 mi · Back Bay 1.9 mi · Brighton 2.5 mi · Chestnut Hill 2.5 mi

United States travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 100% of US
price level, 2025
GDP per capita
$90,027
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
98%
of population, 2024
Homicide rate
5.8
per 100k, 2023
Road deaths
12.7
per 100k/yr, 2019
Income group
High
World Bank
Religion
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Brookline (42.3318°, -71.1212°, elevation 33 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).