August is one of the warmer months of the year in Boston, with average highs near 20.9°C and lows around 12.4°C (mean 16.7°C). It is about average for rainfall, averaging 60 mm of rainfall and 80% relative humidity across the period.
August is one of the warmer months of the year in Boston. Across 45 years of records, the warmest August in Boston was 1997 — when the month averaged 19°C — while the coldest was 1986 at 13.8°C. Typical August days reach 20.9°C with nights near 12.4°C. The long-term trend is warming, about 0.3°C per decade.
August is about average for rainfall in Boston, averaging 60 mm of rainfall. The wettest August on record was 2004 with 144 mm, while the driest was 1995 at 10 mm.
Relative humidity in Boston during August averages 80%. The most humid Augusts were 2002 and 2004 at 84%, and the least humid was 1992 at 75%.
August receives about 4.2 kWh/m²/day of solar energy in Boston. The sunniest August was 1995 at 5 kWh/m²/day, and the cloudiest were 1986 and 1987 at 3.4.
Average wind speed in Boston during August is 3.3 m/s. The windiest August was 1985 at 4.5 m/s, while the calmest were 1984 and 2002 at 2.5 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 15.8°C | 16.8°C | 16.9°C | 16.6°C | 17.5°C | +1.7°C |
| Avg High | 20.0°C | 21.2°C | 21.0°C | 20.8°C | 21.8°C | +1.8°C |
| Avg Low | 11.6°C | 12.5°C | 12.8°C | 12.4°C | 13.3°C | +1.7°C |
| Avg Rain | 57 mm | 53 mm | 73 mm | 66 mm | 44 mm | -12 mm |
August temperatures in Boston have risen by about 1.2°C between 1981–1985 and 2021–2025.
August has ranged from a record low of 6.5°C (1986) to a record high of 30.9°C (1990).
Rainfall in August is about average for rainfall, averaging 60 mm, with a wettest year of 144 mm.
One of the best times to visit Boston
August is one of the best times to visit Boston. Expect days averaging 20.9°C and nights around 12.4°C (mean 16.7°C) — warmer than Boston's yearly average — with moderate rainfall (60 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 22.2°C | 17.6°C | 13.0°C | 27.7°C | 10.3°C | 18 mm | 76% | 3.4 m/s | 4.4 |
| 2024 | 22.0°C | 17.4°C | 12.8°C | 28.6°C | 9.9°C | 30 mm | 79% | 3.6 m/s | 4.2 |
| 2023 | 21.3°C | 17.0°C | 12.7°C | 25.5°C | 9.3°C | 56 mm | 80% | 3.3 m/s | 4.3 |
| 2022 | 23.3°C | 18.8°C | 14.2°C | 28.3°C | 9.7°C | 49 mm | 78% | 2.7 m/s | 4.9 |
| 2021 | 20.1°C | 16.4°C | 12.7°C | 22.7°C | 10.0°C | 33 mm | 82% | 3.4 m/s | 3.7 |
| 2020 | 21.8°C | 18.0°C | 14.1°C | 29.3°C | 8.0°C | 80 mm | 81% | 4 m/s | 4 |
| 2019 | 22.3°C | 17.6°C | 13.0°C | 28.6°C | 9.9°C | 62 mm | 78% | 3.9 m/s | 4.5 |
| 2018 | 21.6°C | 17.3°C | 13.1°C | 26.7°C | 9.0°C | 60 mm | 79% | 3 m/s | 4.2 |
| 2017 | 19.9°C | 15.8°C | 11.8°C | 24.4°C | 8.2°C | 84 mm | 81% | 3.3 m/s | 4.2 |
| 2016 | 21.3°C | 17.1°C | 12.9°C | 26.2°C | 9.4°C | 46 mm | 81% | 3.5 m/s | 4.6 |
| 2015 | 20.7°C | 16.4°C | 12.1°C | 26.6°C | 9.1°C | 75 mm | 80% | 3.4 m/s | 3.9 |
| 2014 | 19.3°C | 15.4°C | 11.4°C | 22.7°C | 7.1°C | 82 mm | 79% | 3.9 m/s | 4 |
| 2013 | 21.4°C | 17.0°C | 12.6°C | 27.7°C | 9.2°C | 42 mm | 80% | 3.2 m/s | 4.3 |
| 2012 | 21.2°C | 17.1°C | 12.9°C | 27.0°C | 7.8°C | 58 mm | 80% | 3.2 m/s | 4 |
| 2011 | 20.6°C | 16.2°C | 11.8°C | 26.7°C | 8.4°C | 50 mm | 77% | 3.3 m/s | 3.9 |
| 2010 | 19.6°C | 15.7°C | 11.9°C | 23.8°C | 8.7°C | 100 mm | 81% | 3.8 m/s | 3.9 |
| 2009 | 21.5°C | 17.3°C | 13.0°C | 25.4°C | 9.2°C | 45 mm | 81% | 3.5 m/s | 4.2 |
| 2008 | 20.8°C | 17.0°C | 13.2°C | 23.8°C | 10.1°C | 96 mm | 83% | 3.8 m/s | 3.5 |
| 2007 | 20.2°C | 16.0°C | 11.8°C | 25.8°C | 9.2°C | 48 mm | 81% | 3.5 m/s | 4.5 |
| 2006 | 19.8°C | 16.1°C | 12.4°C | 25.8°C | 9.9°C | 116 mm | 82% | 3.6 m/s | 3.7 |
| 2005 | 20.5°C | 16.1°C | 11.7°C | 27.3°C | 9.3°C | 67 mm | 81% | 3.1 m/s | 4.4 |
| 2004 🌧️ | 21.4°C | 17.5°C | 13.7°C | 26.5°C | 9.1°C | 144 mm | 84% | 3.1 m/s | 4.1 |
| 2003 | 22.0°C | 17.7°C | 13.5°C | 30.5°C | 7.9°C | 16 mm | 81% | 2.6 m/s | 4.5 |
| 2002 | 21.5°C | 17.4°C | 13.4°C | 27.1°C | 10.8°C | 73 mm | 84% | 2.5 m/s | 3.8 |
| 2001 | 21.1°C | 17.0°C | 12.8°C | 27.6°C | 8.7°C | 74 mm | 82% | 2.9 m/s | 4 |
| 2000 | 20.7°C | 16.5°C | 12.4°C | 24.0°C | 8.7°C | 47 mm | 82% | 2.8 m/s | 4.3 |
| 1999 | 20.0°C | 16.1°C | 12.3°C | 27.2°C | 8.0°C | 100 mm | 81% | 3 m/s | 3.9 |
| 1998 | 20.3°C | 15.8°C | 11.2°C | 25.1°C | 7.9°C | 51 mm | 80% | 3.5 m/s | 4.5 |
| 1997 🔥 | 23.3°C | 19.0°C | 14.8°C | 27.5°C | 10.1°C | 73 mm | 81% | 2.9 m/s | 4.2 |
| 1996 | 20.9°C | 16.6°C | 12.2°C | 27.0°C | 9.3°C | 84 mm | 79% | 3.3 m/s | 4.1 |
| 1995 | 22.0°C | 17.7°C | 13.4°C | 26.4°C | 10.0°C | 10 mm | 79% | 3.1 m/s | 5 |
| 1994 | 20.0°C | 16.0°C | 12.1°C | 25.3°C | 8.3°C | 40 mm | 80% | 3.5 m/s | 4.3 |
| 1993 | 19.1°C | 14.9°C | 10.6°C | 23.0°C | 7.3°C | 52 mm | 79% | 3.4 m/s | 4.3 |
| 1992 | 20.7°C | 16.3°C | 11.8°C | 25.2°C | 8.6°C | 79 mm | 75% | 4.3 m/s | 4.2 |
| 1991 | 22.6°C | 17.7°C | 12.8°C | 25.6°C | 8.6°C | 16 mm | 76% | 3 m/s | 4.6 |
| 1990 | 23.3°C | 18.3°C | 13.3°C | 30.9°C | 9.8°C | 28 mm | 76% | 3.2 m/s | 4.6 |
| 1989 | 21.3°C | 16.7°C | 12.1°C | 25.4°C | 9.6°C | 44 mm | 77% | 3.6 m/s | 4.6 |
| 1988 | 19.7°C | 15.5°C | 11.3°C | 24.8°C | 8.5°C | 46 mm | 80% | 3.6 m/s | 4.1 |
| 1987 | 19.4°C | 15.5°C | 11.7°C | 26.2°C | 6.9°C | 72 mm | 83% | 3.1 m/s | 3.4 |
| 1986 ❄️ | 17.7°C | 13.8°C | 9.9°C | 21.8°C | 6.5°C | 101 mm | 81% | 3.7 m/s | 3.4 |
| 1985 | 18.9°C | 14.8°C | 10.7°C | 22.7°C | 9.0°C | 62 mm | 81% | 4.5 m/s | 3.8 |
| 1984 | 21.6°C | 17.2°C | 12.8°C | 25.3°C | 8.5°C | 50 mm | 80% | 2.5 m/s | 4.6 |
| 1983 | 21.2°C | 16.8°C | 12.5°C | 24.9°C | 7.9°C | 24 mm | 81% | 2.7 m/s | — |
| 1982 | 20.0°C | 15.9°C | 11.8°C | 25.7°C | 7.5°C | 61 mm | 81% | 3.7 m/s | — |
| 1981 | 20.4°C | 16.2°C | 12.0°C | 25.0°C | 8.5°C | 52 mm | 81% | 2.8 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 20.9°C with lows near 12.4°C (mean 16.7°C), based on 45 years of NASA POWER data.
August averages 60 mm of rainfall in Boston, about average for rainfall. The wettest on record was 144 mm in 2004.
The hottest August reached 30.9°C in 1990. The coldest dipped to 6.5°C in 1986.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have risen by about 1.2°C. Daytime highs moved from 20.4°C to 21.8°C and overnight lows from 12°C to 13.1°C over the same span.
August is one of the warmer months of the year in Boston and about average for rainfall, so plan for around 20.9°C daytime highs and 12.4°C at night.
Not quite — August is the 12th coolest month in Boston, averaging 16.7°C.
For August in Boston, pack light layers you can adjust through the day, with typical highs of 20.9°C and lows of 12.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in August averages 80% — quite humid.
Average wind speed in August is 3.3 m/s. The windiest August on record averaged 4.5 m/s (1985).
The wettest August on record was 2004 with 144 mm. On average, August sees 60 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Boston behaves each August, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for August specifically, along with year-by-year records and how the month has changed over the decades.
