Boston weather in September: Boston, Massachusetts: normal highs, lows, rain and records for September
Boston in September has a normal high of 73°F and a normal low of 58°F, a daily mean of 66°F, falling from 78°F on the 1st to 68°F by the 30th. Measurable precipitation falls on 9 days in a normal September, 3.56 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 23°C and low of 15°C, 90 mm of precipitation in September.
- NOAA stationBoston Logan International Airport
- Station IDUSW00014739
- Location42.36°N 71.01°W
- Elevation12 ft (4 m)
- From the center2 miles
- Population673,458
- Jan 37° 23°
- Feb 39° 25°
- Mar 46° 31°
- Apr 56° 41°
- May 67° 50°
- Jun 76° 60°
- Jul 82° 66°
- Aug 80° 65°
- Sep 73° 58°
- Oct 62° 48°
- Nov 52° 38°
- Dec 42° 29°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Boston in September?
The normal high is 73°F and the normal low 58°F, for a daily mean of 65.6°F. September is 7.1°F cooler than August and 10.8°F warmer than October. September is the 4th warmest month of the year in Boston and the 7th wettest. Across the month the normal high falls 10°F, from 78°F on September 1 to 68°F on September 30. From one year to the next September's mean temperature typically moves about 1.9°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 64°F and 68°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 32%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 78°F | 63°F | 28% | 18% |
| September 8 | 76°F | 61°F | 28% | 18% |
| September 15 | 74°F | 59°F | 29% | 19% |
| September 22 | 71°F | 56°F | 31% | 19% |
| September 30 | 68°F | 53°F | 32% | 20% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 78°F | 63°F | 28% | 18% | 13 h 10 min |
| September 2 | 78°F | 62°F | 28% | 18% | 13 h 10 min |
| September 3 | 77°F | 62°F | 28% | 18% | 13 h 10 min |
| September 4 | 77°F | 62°F | 28% | 18% | 13 h |
| September 5 | 77°F | 62°F | 28% | 18% | 13 h |
| September 6 | 76°F | 61°F | 28% | 18% | 13 h |
| September 7 | 76°F | 61°F | 28% | 18% | 13 h |
| September 8 | 76°F | 61°F | 28% | 18% | 12 h 50 min |
| September 9 | 76°F | 61°F | 29% | 18% | 12 h 50 min |
| September 10 | 75°F | 60°F | 29% | 18% | 12 h 50 min |
| September 11 | 75°F | 60°F | 29% | 18% | 12 h 40 min |
| September 12 | 75°F | 60°F | 29% | 19% | 12 h 40 min |
| September 13 | 74°F | 59°F | 29% | 19% | 12 h 40 min |
| September 14 | 74°F | 59°F | 29% | 19% | 12 h 40 min |
| September 15 | 74°F | 59°F | 29% | 19% | 12 h 30 min |
| September 16 | 73°F | 58°F | 29% | 19% | 12 h 30 min |
| September 17 | 73°F | 58°F | 30% | 19% | 12 h 30 min |
| September 18 | 72°F | 58°F | 30% | 19% | 12 h 30 min |
| September 19 | 72°F | 57°F | 30% | 19% | 12 h 20 min |
| September 20 | 72°F | 57°F | 30% | 19% | 12 h 20 min |
| September 21 | 71°F | 56°F | 30% | 19% | 12 h 20 min |
| September 22 | 71°F | 56°F | 31% | 19% | 12 h 10 min |
| September 23 | 71°F | 56°F | 31% | 20% | 12 h 10 min |
| September 24 | 70°F | 55°F | 31% | 20% | 12 h 10 min |
| September 25 | 70°F | 55°F | 31% | 20% | 12 h 10 min |
| September 26 | 69°F | 55°F | 31% | 20% | 12 h |
| September 27 | 69°F | 54°F | 32% | 20% | 12 h |
| September 28 | 69°F | 54°F | 32% | 20% | 12 h |
| September 29 | 68°F | 53°F | 32% | 20% | 11 h 50 min |
| September 30 | 68°F | 53°F | 32% | 20% | 11 h 50 min |
- Normal high
- 73°FSeptember average
- Normal low
- 58°FSeptember average
- Precipitation
- 3.56 inmonth total
- Days with precipitation
- 90.01 inch or more
- Days at 90°F or more
- 1
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 20
- Days at 80°F or more
- 7
- Sunshine
- 77%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00014739; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Boston in September?
On a given September day the chance of 0.01 inch or more is 30% on average, highest around September 30 (32%). In all, 3.56 in falls on 9 days of a normal September, 1 of them with an inch or more.
In a normal September in Boston, 1 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00014739.
How humid and windy is Boston in September?
At 3 p.m. the normal temperature is 66°F with 59% relative humidity and a dew point of 51°F; at 6 a.m. it is 56°F with 81% humidity. The wind averages 10.5 mph, most often from the southwest in the afternoon.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 56°F | 50°F | 81% | 9.3 mph | 48% |
| 9 a.m. | 62°F | 51°F | 68% | 10.7 mph | 43% |
| noon | 65°F | 51°F | 59% | 12.4 mph | 35% |
| 3 p.m. | 66°F | 51°F | 59% | 12.9 mph | 32% |
| 6 p.m. | 62°F | 51°F | 66% | 10.5 mph | 42% |
| 9 p.m. | 60°F | 51°F | 72% | 9.6 mph | 52% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00014739. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for September in Boston?
The warmest September temperature on Boston's official record (since 1872) is 102°F, on September 7, 1881; the coldest is 34°F, on September 26, 1879. The wettest September brought 10.94 in (1933).
The September mean against the 1991-2020 normal of 65.6°F: 2021 69.7°F (+4.1), 2022 65.2°F (−0.4), 2023 67.4°F (+1.8), 2024 65.8°F (+0.3), 2025 66.5°F (+0.9), 2026 64.6°F (−1.0). 4 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 69.7°F | +4.1°F | 7.47 in |
| 2022 | 65.2°F | −0.4°F | 2.60 in |
| 2023 | 67.4°F | +1.8°F | 3.75 in |
| 2024 | 65.8°F | +0.3°F | 1.33 in |
| 2025 | 66.5°F | +0.9°F | 3.09 in |
| 2026 | 64.6°F | −1.0°F | 5.35 in |
Source: records: ACIS, NWS threaded record BOSthr; recent months: ACIS, station USW00014739. Records and recent months use complete months only.
How does September in Boston compare across Massachusetts?
Across the 35 places PlainClimate covers in Massachusetts, September normal highs run from 70°F in East Sandwich to 78°F in Maynard; Boston's is 73°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.