May is one of the warmer months of the year in Boston, with average highs near 15.5°C and lows around 7.3°C (mean 11.4°C). It is about average for rainfall, averaging 54 mm of rainfall and 81% relative humidity across the period.
May is one of the warmer months of the year in Boston. Across 45 years of records, the warmest Mays in Boston were 1992 and 2024 — when the month averaged 13.4°C — while the coldest was 1996 at 8.7°C. Typical May days reach 15.5°C with nights near 7.3°C. The long-term trend is warming, about 0.3°C per decade.
May is about average for rainfall in Boston, averaging 54 mm of rainfall. The wettest May on record was 2007 with 113 mm, while the driest was 2020 at 8 mm.
Relative humidity in Boston during May averages 81%. The most humid May was 1981 at 85%, and the least humid was 1992 at 75%.
May receives about 4.8 kWh/m²/day of solar energy in Boston. The sunniest May was 2020 at 6.1 kWh/m²/day, and the cloudiest was 1991 at 4.
Average wind speed in Boston during May is 3.4 m/s. The windiest May was 1986 at 4.3 m/s, while the calmest were 1990 and 2004 at 2.6 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 10.6°C | 11.3°C | 11.7°C | 11.5°C | 12.1°C | +1.5°C |
| Avg High | 14.6°C | 15.6°C | 15.7°C | 15.7°C | 16.3°C | +1.7°C |
| Avg Low | 6.5°C | 7.1°C | 7.6°C | 7.3°C | 7.9°C | +1.4°C |
| Avg Rain | 61 mm | 39 mm | 64 mm | 56 mm | 51 mm | -10 mm |
May temperatures in Boston have risen by about 1.8°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -0.6°C (1982) to a record high of 25.5°C (1992).
Rainfall in May is about average for rainfall, averaging 54 mm, with a wettest year of 113 mm.
A good time to visit Boston
May is a good time to visit Boston, with days averaging 15.5°C and nights around 7.3°C (mean 11.4°C, warmer than Boston's yearly average) and moderate rainfall. August and July are marginally more temperate, but May still suits most travellers.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 17.0°C | 12.5°C | 8.1°C | 23.1°C | 5.0°C | 29 mm | 79% | 3.4 m/s | 5.5 |
| 2024 | 17.4°C | 13.4°C | 9.5°C | 20.7°C | 7.2°C | 70 mm | 85% | 3 m/s | 4.5 |
| 2023 | 16.0°C | 12.0°C | 8.0°C | 19.5°C | 3.8°C | 47 mm | 82% | 2.9 m/s | 5.1 |
| 2022 | 17.0°C | 12.8°C | 8.6°C | 21.6°C | 4.7°C | 52 mm | 81% | 3.1 m/s | 5 |
| 2021 | 13.6°C | 9.9°C | 6.1°C | 19.5°C | 1.4°C | 100 mm | 83% | 3.5 m/s | 4.5 |
| 2020 | 16.7°C | 12.0°C | 7.3°C | 23.7°C | 1.5°C | 8 mm | 77% | 3.1 m/s | 6.1 |
| 2019 | 15.4°C | 11.2°C | 7.0°C | 21.5°C | 2.9°C | 46 mm | 79% | 2.8 m/s | 5.1 |
| 2018 | 17.3°C | 12.5°C | 7.7°C | 22.7°C | 1.8°C | 49 mm | 81% | 3.2 m/s | 5.6 |
| 2017 | 16.9°C | 12.7°C | 8.6°C | 23.8°C | 2.0°C | 70 mm | 82% | 3.4 m/s | 4.8 |
| 2016 | 15.8°C | 11.7°C | 7.5°C | 21.5°C | 1.0°C | 53 mm | 81% | 3.5 m/s | 5 |
| 2015 | 14.7°C | 10.7°C | 6.7°C | 18.8°C | 1.8°C | 73 mm | 78% | 3.9 m/s | 4.8 |
| 2014 | 16.1°C | 12.3°C | 8.6°C | 21.4°C | 2.5°C | 100 mm | 81% | 3.2 m/s | 4.6 |
| 2013 | 14.2°C | 10.2°C | 6.1°C | 18.8°C | 1.3°C | 63 mm | 80% | 3.7 m/s | 4.6 |
| 2012 | 15.4°C | 11.5°C | 7.5°C | 24.1°C | 2.5°C | 49 mm | 80% | 3.4 m/s | 4.7 |
| 2011 | 16.4°C | 12.1°C | 7.7°C | 19.4°C | 3.6°C | 40 mm | 75% | 4 m/s | 5.1 |
| 2010 | 14.3°C | 10.1°C | 6.0°C | 23.5°C | 1.8°C | 21 mm | 78% | 2.9 m/s | 5.1 |
| 2009 | 15.8°C | 11.9°C | 8.0°C | 20.6°C | 4.1°C | 58 mm | 81% | 3.9 m/s | 5.2 |
| 2008 | 16.8°C | 12.5°C | 8.2°C | 23.1°C | 3.9°C | 37 mm | 82% | 3.5 m/s | 4.7 |
| 2007 🌧️ | 15.0°C | 11.4°C | 7.7°C | 21.3°C | 3.1°C | 113 mm | 82% | 3.4 m/s | 4.3 |
| 2006 | 16.0°C | 11.9°C | 7.9°C | 21.7°C | 3.8°C | 95 mm | 81% | 3.6 m/s | 4.5 |
| 2005 | 14.9°C | 10.9°C | 6.8°C | 24.3°C | 2.6°C | 36 mm | 79% | 3.7 m/s | 5.2 |
| 2004 | 15.9°C | 11.7°C | 7.4°C | 20.9°C | 4.1°C | 43 mm | 81% | 2.6 m/s | 4.8 |
| 2003 | 15.8°C | 11.7°C | 7.6°C | 23.4°C | 2.5°C | 56 mm | 82% | 3.6 m/s | 4.6 |
| 2002 | 15.7°C | 11.8°C | 7.9°C | 21.8°C | 3.3°C | 61 mm | 82% | 3.9 m/s | 4.4 |
| 2001 | 15.9°C | 11.5°C | 7.0°C | 21.5°C | 2.6°C | 46 mm | 82% | 3 m/s | 5.1 |
| 2000 | 15.2°C | 11.4°C | 7.6°C | 23.0°C | 5.1°C | 93 mm | 84% | 3.4 m/s | 4.7 |
| 1999 | 16.7°C | 12.6°C | 8.6°C | 22.0°C | 6.0°C | 36 mm | 81% | 3.6 m/s | 4.6 |
| 1998 | 16.3°C | 12.0°C | 7.7°C | 21.3°C | 2.1°C | 24 mm | 83% | 3.1 m/s | 5.4 |
| 1997 | 15.6°C | 11.1°C | 6.6°C | 21.6°C | 1.1°C | 47 mm | 79% | 3.1 m/s | 5.2 |
| 1996 ❄️ | 12.5°C | 8.7°C | 4.9°C | 20.2°C | 0.7°C | 46 mm | 78% | 3.9 m/s | 4.3 |
| 1995 | 15.6°C | 11.1°C | 6.7°C | 22.8°C | 1.2°C | 47 mm | 79% | 3.3 m/s | 4.6 |
| 1994 | 13.9°C | 10.3°C | 6.6°C | 18.7°C | 3.7°C | 61 mm | 81% | 3.3 m/s | 4.5 |
| 1993 | 15.4°C | 11.3°C | 7.2°C | 20.5°C | 1.4°C | 60 mm | 79% | 4.1 m/s | 4.6 |
| 1992 🔥 | 18.4°C | 13.4°C | 8.3°C | 25.5°C | 3.5°C | 28 mm | 75% | 3.3 m/s | 5.6 |
| 1991 | 14.5°C | 10.5°C | 6.5°C | 20.2°C | 2.0°C | 16 mm | 78% | 3.3 m/s | 4 |
| 1990 | 16.9°C | 12.2°C | 7.5°C | 22.7°C | 5.5°C | 21 mm | 77% | 2.6 m/s | 5.3 |
| 1989 | 17.1°C | 12.1°C | 7.1°C | 24.6°C | 2.7°C | 15 mm | 81% | 2.9 m/s | 5.6 |
| 1988 | 15.2°C | 11.3°C | 7.5°C | 19.7°C | 3.8°C | 49 mm | 83% | 3.2 m/s | 4.7 |
| 1987 | 13.3°C | 9.3°C | 5.3°C | 19.2°C | 2.7°C | 48 mm | 82% | 3.7 m/s | 4.2 |
| 1986 | 15.0°C | 10.9°C | 6.8°C | 18.9°C | 4.6°C | 84 mm | 82% | 4.3 m/s | 4.2 |
| 1985 | 14.5°C | 10.7°C | 6.9°C | 21.7°C | 3.0°C | 69 mm | 83% | 3.4 m/s | 4.1 |
| 1984 | 13.3°C | 9.4°C | 5.5°C | 18.4°C | 2.8°C | 70 mm | 81% | 3.3 m/s | 4.4 |
| 1983 | 13.1°C | 9.6°C | 6.0°C | 16.6°C | 3.1°C | 78 mm | 85% | 3.1 m/s | — |
| 1982 | 15.5°C | 11.0°C | 6.5°C | 22.7°C | -0.6°C | 47 mm | 79% | 3.1 m/s | — |
| 1981 | 14.7°C | 10.9°C | 7.1°C | 19.1°C | 0.8°C | 88 mm | 85% | 3.3 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 15.5°C with lows near 7.3°C (mean 11.4°C), based on 45 years of NASA POWER data.
May averages 54 mm of rainfall in Boston, about average for rainfall. The wettest on record was 113 mm in 2007.
The hottest May reached 25.5°C in 1992. The coldest dipped to -0.6°C in 1982.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.8°C. Daytime highs moved from 14.2°C to 16.2°C and overnight lows from 6.4°C to 8.1°C over the same span.
May is one of the warmer months of the year in Boston and about average for rainfall, so plan for around 15.5°C daytime highs and 7.3°C at night.
Not quite — May is the 8th coolest month in Boston, averaging 11.4°C.
For May in Boston, pack warm layers and a jacket for chilly mornings, with typical highs of 15.5°C and lows of 7.3°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 81% — quite humid.
Average wind speed in May is 3.4 m/s. The windiest May on record averaged 4.3 m/s (1986).
The wettest May on record was 2007 with 113 mm. On average, May sees 54 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 May, 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 May specifically, along with year-by-year records and how the month has changed over the decades.
