May is one of the warmer months of the year in Washington, with average highs near 22.3°C and lows around 11.8°C (mean 17.1°C). It is a relatively wet time of year, averaging 107 mm of rainfall and 77% relative humidity across the period.
May is one of the warmer months of the year in Washington. Across 45 years of records, the warmest May in Washington was 2018 — when the month averaged 20.3°C — while the coldest were 1992, 1994 and 1997 at 14.4°C. Typical May days reach 22.3°C with nights near 11.8°C. The long-term trend is warming, about 0.5°C per decade.
May is a relatively wet time of year in Washington, averaging 107 mm of rainfall. The wettest May on record was 2018 with 211 mm, while the driest was 2007 at 32 mm.
Relative humidity in Washington during May averages 77%. The most humid May was 2003 at 85%, and the least humid was 1999 at 68%.
May receives about 5.5 kWh/m²/day of solar energy in Washington. The sunniest May was 2015 at 6.4 kWh/m²/day, and the cloudiest was 2003 at 4.
Average wind speed in Washington during May is 2.5 m/s. The windiest May was 1997 at 3.2 m/s, while the calmest were 1982 and 2016 at 2.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.4°C | 16.2°C | 16.9°C | 18.3°C | 17.4°C | +1°C |
| Avg High | 21.9°C | 21.6°C | 22.3°C | 23.3°C | 22.6°C | +0.7°C |
| Avg Low | 11.0°C | 10.8°C | 11.6°C | 13.4°C | 12.2°C | +1.2°C |
| Avg Rain | 122 mm | 94 mm | 108 mm | 113 mm | 96 mm | -27 mm |
May temperatures in Washington have risen by about 1.4°C between 1981–1985 and 2021–2025.
May has ranged from a record low of 0.4°C (2020) to a record high of 33.5°C (1991).
Rainfall in May is a relatively wet time of year, averaging 107 mm, with a wettest year of 211 mm.
A good time to visit Washington
May is a good time to visit Washington, with days averaging 22.3°C and nights around 11.8°C (mean 17.1°C, warmer than Washington's yearly average) and higher rainfall. June and September 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 | 23.1°C | 18.4°C | 13.7°C | 28.9°C | 8.0°C | 175 mm | 76% | 2.7 m/s | 5.1 |
| 2024 | 23.5°C | 18.9°C | 14.4°C | 28.8°C | 7.5°C | 94 mm | 82% | 2.2 m/s | 5.1 |
| 2023 | 22.7°C | 16.8°C | 10.9°C | 28.4°C | 4.9°C | 33 mm | 68% | 2.4 m/s | 6 |
| 2022 | 23.2°C | 18.0°C | 12.8°C | 33.3°C | 4.5°C | 134 mm | 79% | 2.6 m/s | 5.1 |
| 2021 | 22.5°C | 16.9°C | 11.2°C | 30.4°C | 4.5°C | 78 mm | 74% | 2.5 m/s | 5.9 |
| 2020 | 20.7°C | 15.5°C | 10.4°C | 26.8°C | 0.4°C | 59 mm | 76% | 3 m/s | 5.4 |
| 2019 | 24.2°C | 19.5°C | 14.8°C | 29.6°C | 6.1°C | 140 mm | 82% | 2.5 m/s | 5.8 |
| 2018 🔥 🌧️ | 25.1°C | 20.3°C | 15.4°C | 29.2°C | 6.3°C | 211 mm | 83% | 2.3 m/s | 5.4 |
| 2017 | 22.1°C | 17.0°C | 12.0°C | 30.7°C | 4.5°C | 150 mm | 76% | 3 m/s | 5.2 |
| 2016 | 20.4°C | 16.0°C | 11.6°C | 29.1°C | 4.2°C | 141 mm | 82% | 2.1 m/s | 4.6 |
| 2015 | 24.7°C | 19.4°C | 14.2°C | 29.9°C | 7.7°C | 64 mm | 78% | 2.2 m/s | 6.4 |
| 2014 | 22.6°C | 17.4°C | 12.3°C | 28.6°C | 6.7°C | 108 mm | 80% | 2.3 m/s | 5.9 |
| 2013 | 22.4°C | 17.0°C | 11.6°C | 30.9°C | 2.7°C | 75 mm | 78% | 2.7 m/s | 5.8 |
| 2012 | 25.1°C | 20.0°C | 14.9°C | 30.8°C | 7.2°C | 91 mm | 78% | 2.3 m/s | 5.8 |
| 2011 | 23.6°C | 18.7°C | 13.7°C | 32.4°C | 6.0°C | 74 mm | 81% | 2.4 m/s | 5.6 |
| 2010 | 23.3°C | 18.1°C | 13.0°C | 29.6°C | 3.3°C | 79 mm | 79% | 2.5 m/s | 5.6 |
| 2009 | 22.2°C | 17.4°C | 12.6°C | 27.3°C | 6.8°C | 165 mm | 81% | 2.5 m/s | 5.2 |
| 2008 | 21.2°C | 15.7°C | 10.2°C | 26.8°C | 5.5°C | 185 mm | 78% | 2.8 m/s | 5.7 |
| 2007 | 23.2°C | 17.7°C | 12.1°C | 30.0°C | 4.0°C | 32 mm | 75% | 2.2 m/s | 6.2 |
| 2006 | 23.3°C | 17.4°C | 11.4°C | 32.9°C | 5.6°C | 50 mm | 68% | 2.5 m/s | 6 |
| 2005 | 19.9°C | 14.6°C | 9.4°C | 27.4°C | 2.3°C | 90 mm | 77% | 2.4 m/s | 5.5 |
| 2004 | 24.8°C | 19.9°C | 14.9°C | 29.4°C | 4.2°C | 105 mm | 82% | 2.2 m/s | 5.8 |
| 2003 | 19.2°C | 15.1°C | 11.0°C | 25.2°C | 5.6°C | 177 mm | 85% | 2.4 m/s | 4 |
| 2002 | 23.5°C | 17.1°C | 10.7°C | 31.5°C | 3.9°C | 85 mm | 68% | 2.8 m/s | 6.2 |
| 2001 | 22.9°C | 17.1°C | 11.4°C | 29.5°C | 4.8°C | 112 mm | 72% | 2.2 m/s | 5.5 |
| 2000 | 23.2°C | 17.5°C | 11.9°C | 30.3°C | 5.1°C | 79 mm | 78% | 2.4 m/s | 5.5 |
| 1999 | 23.5°C | 17.2°C | 10.9°C | 32.4°C | 4.7°C | 37 mm | 68% | 2.5 m/s | 6.3 |
| 1998 | 22.6°C | 17.9°C | 13.2°C | 29.9°C | 7.4°C | 116 mm | 82% | 2.2 m/s | 5.3 |
| 1997 | 20.2°C | 14.4°C | 8.7°C | 29.3°C | 4.0°C | 61 mm | 73% | 3.2 m/s | 6.2 |
| 1996 | 20.3°C | 15.3°C | 10.3°C | 30.2°C | 2.6°C | 143 mm | 80% | 2.5 m/s | 5 |
| 1995 | 21.8°C | 16.3°C | 10.9°C | 28.8°C | 4.2°C | 102 mm | 74% | 2.6 m/s | 5.3 |
| 1994 | 20.1°C | 14.4°C | 8.8°C | 28.3°C | 3.8°C | 75 mm | 77% | 2.9 m/s | 5.9 |
| 1993 | 22.1°C | 16.8°C | 11.6°C | 28.1°C | 6.4°C | 82 mm | 80% | 2.3 m/s | 5.7 |
| 1992 ❄️ | 19.8°C | 14.4°C | 9.0°C | 28.1°C | 3.4°C | 94 mm | 77% | 2.5 m/s | 5.3 |
| 1991 | 24.8°C | 19.5°C | 14.2°C | 33.5°C | 6.2°C | 50 mm | 77% | 2.2 m/s | 6 |
| 1990 | 20.9°C | 15.7°C | 10.5°C | 26.4°C | 6.7°C | 175 mm | 78% | 2.9 m/s | 5.1 |
| 1989 | 20.3°C | 15.6°C | 10.9°C | 28.5°C | 4.2°C | 206 mm | 82% | 2.6 m/s | 4.9 |
| 1988 | 21.6°C | 16.5°C | 11.5°C | 29.4°C | 4.4°C | 151 mm | 81% | 2.4 m/s | 5.5 |
| 1987 | 22.0°C | 16.5°C | 11.0°C | 30.8°C | 3.7°C | 92 mm | 81% | 2.2 m/s | 5.5 |
| 1986 | 23.0°C | 17.2°C | 11.3°C | 30.8°C | 1.7°C | 34 mm | 73% | 2.4 m/s | 5.8 |
| 1985 | 23.1°C | 17.3°C | 11.6°C | 28.6°C | 3.6°C | 135 mm | 73% | 2.6 m/s | 5.8 |
| 1984 | 20.3°C | 15.1°C | 10.0°C | 27.3°C | 3.6°C | 144 mm | 82% | 2.9 m/s | 4.5 |
| 1983 | 20.7°C | 15.4°C | 10.1°C | 25.8°C | 1.5°C | 145 mm | 80% | 2.7 m/s | — |
| 1982 | 23.7°C | 18.1°C | 12.5°C | 28.1°C | 6.4°C | 87 mm | 78% | 2.1 m/s | — |
| 1981 | 22.1°C | 16.1°C | 10.1°C | 30.3°C | 3.1°C | 108 mm | 74% | 2.5 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 22.3°C with lows near 11.8°C (mean 17.1°C), based on 45 years of NASA POWER data.
May averages 107 mm of rainfall in Washington, a relatively wet time of year. The wettest on record was 211 mm in 2018.
The hottest May reached 33.5°C in 1991. The coldest dipped to 0.4°C in 2020.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.4°C. Daytime highs moved from 22°C to 23°C and overnight lows from 10.9°C to 12.6°C over the same span.
May is one of the warmer months of the year in Washington and a relatively wet time of year, so plan for around 22.3°C daytime highs and 11.8°C at night.
Not quite — May is the 8th coolest month in Washington, averaging 17.1°C.
For May in Washington, pack light layers you can adjust through the day, with typical highs of 22.3°C and lows of 11.8°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 77% — quite humid.
Average wind speed in May is 2.5 m/s. The windiest May on record averaged 3.2 m/s (1997).
The wettest May on record was 2018 with 211 mm. On average, May sees 107 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 Washington 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.
