May is one of the warmer months of the year in Washington, with average highs near 21.3°C and lows around 9.7°C (mean 15.5°C). It is a relatively wet time of year, averaging 106 mm of rainfall and 78% 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 19.4°C — while the coldest was 1997 at 11.5°C. Typical May days reach 21.3°C with nights near 9.7°C. The long-term trend is warming, about 0.5°C per decade.
May is a relatively wet time of year in Washington, averaging 106 mm of rainfall. The wettest May on record was 2025 with 172 mm, while the driest was 2015 at 46 mm.
Relative humidity in Washington during May averages 78%. The most humid Mays were 1989 and 2011 at 85%, and the least humid was 1999 at 69%.
May receives about 5.3 kWh/m²/day of solar energy in Washington. The sunniest May was 2007 at 6.6 kWh/m²/day, and the cloudiest were 1984 and 1989 at 4.3.
Average wind speed in Washington during May is 0.1 m/s. The windiest Mays were 2021, 2023 and 2024, among others at 0.1 m/s, while the calmest were 2020, 2022 and 2025, among others at 0 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.7°C | 14.7°C | 15.3°C | 16.9°C | 15.6°C | +0.9°C |
| Avg High | 20.6°C | 20.6°C | 21.1°C | 22.4°C | 21.4°C | +0.8°C |
| Avg Low | 8.9°C | 8.8°C | 9.4°C | 11.4°C | 9.8°C | +0.9°C |
| Avg Rain | 115 mm | 102 mm | 108 mm | 99 mm | 108 mm | -7 mm |
May temperatures in Washington have risen by about 1.5°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -5.1°C (2020) to a record high of 33.3°C (2006).
Rainfall in May is a relatively wet time of year, averaging 106 mm, with a wettest year of 172 mm.
A good time to visit Washington
May is a good time to visit Washington, with days averaging 21.3°C and nights around 9.7°C (mean 15.5°C, warmer than Washington's yearly average) and higher 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 🌧️ | 20.9°C | 15.6°C | 10.2°C | 27.1°C | 1.2°C | 172 mm | 79% | 0 m/s | 4.7 |
| 2024 | 23.7°C | 18.2°C | 12.7°C | 29.9°C | 5.1°C | 121 mm | 80% | 0.1 m/s | 5.4 |
| 2023 | 21.2°C | 14.7°C | 8.1°C | 28.0°C | 1.7°C | 66 mm | 71% | 0.1 m/s | 6.1 |
| 2022 | 22.8°C | 16.9°C | 11.0°C | 29.4°C | 1.9°C | 125 mm | 80% | 0 m/s | 5.4 |
| 2021 | 20.8°C | 14.8°C | 8.9°C | 29.0°C | -1.5°C | 88 mm | 74% | 0.1 m/s | 5.4 |
| 2020 | 19.0°C | 13.6°C | 8.1°C | 29.0°C | -5.1°C | 74 mm | 79% | 0 m/s | 5.2 |
| 2019 | 22.8°C | 17.6°C | 12.5°C | 27.9°C | 4.4°C | 110 mm | 83% | 0 m/s | 5 |
| 2018 🔥 | 24.7°C | 19.4°C | 14.2°C | 30.0°C | 2.7°C | 106 mm | 84% | 0.1 m/s | 5.3 |
| 2017 | 20.6°C | 15.3°C | 10.0°C | 27.0°C | -0.1°C | 131 mm | 79% | 0.1 m/s | 5.1 |
| 2016 | 20.4°C | 15.1°C | 9.8°C | 29.2°C | -0.1°C | 96 mm | 79% | 0.1 m/s | 5.4 |
| 2015 | 24.0°C | 18.0°C | 12.0°C | 29.2°C | 2.9°C | 46 mm | 77% | 0.1 m/s | 5.8 |
| 2014 | 21.5°C | 15.8°C | 10.0°C | 27.2°C | 2.1°C | 99 mm | 79% | 0.1 m/s | 5.4 |
| 2013 | 21.5°C | 15.6°C | 9.7°C | 28.7°C | -0.2°C | 66 mm | 77% | 0 m/s | 5.9 |
| 2012 | 24.4°C | 18.6°C | 12.9°C | 30.7°C | 2.7°C | 87 mm | 79% | 0.1 m/s | 6.1 |
| 2011 | 21.8°C | 16.6°C | 11.4°C | 31.3°C | 0.1°C | 116 mm | 85% | 0 m/s | 4.8 |
| 2010 | 22.7°C | 16.9°C | 11.2°C | 30.2°C | 0.5°C | 138 mm | 79% | 0.1 m/s | 5.5 |
| 2009 | 20.8°C | 15.4°C | 10.0°C | 27.4°C | 0.3°C | 127 mm | 78% | 0.1 m/s | 5.5 |
| 2008 | 18.9°C | 13.3°C | 7.6°C | 25.8°C | 3.5°C | 149 mm | 79% | 0.1 m/s | 5.1 |
| 2007 | 23.5°C | 16.6°C | 9.8°C | 31.1°C | 2.6°C | 53 mm | 74% | 0.1 m/s | 6.6 |
| 2006 | 20.2°C | 14.3°C | 8.5°C | 33.3°C | 0.9°C | 89 mm | 77% | 0.1 m/s | 5.3 |
| 2005 | 18.9°C | 13.2°C | 7.5°C | 25.7°C | -0.9°C | 81 mm | 77% | 0.1 m/s | 5.7 |
| 2004 | 23.7°C | 18.0°C | 12.3°C | 27.8°C | -1.7°C | 125 mm | 83% | 0 m/s | 5.2 |
| 2003 | 19.8°C | 15.0°C | 10.1°C | 24.2°C | 3.8°C | 154 mm | 83% | 0 m/s | 4.5 |
| 2002 | 20.6°C | 14.1°C | 7.6°C | 29.8°C | -1.7°C | 114 mm | 76% | 0.1 m/s | 5.2 |
| 2001 | 22.2°C | 15.9°C | 9.6°C | 29.3°C | 3.8°C | 88 mm | 72% | 0.1 m/s | 5.1 |
| 2000 | 22.8°C | 16.7°C | 10.6°C | 28.0°C | 3.5°C | 99 mm | 76% | 0.1 m/s | 5.2 |
| 1999 | 23.2°C | 16.2°C | 9.2°C | 30.4°C | 4.1°C | 73 mm | 69% | 0.1 m/s | 6.2 |
| 1998 | 22.9°C | 17.3°C | 11.7°C | 30.8°C | 5.7°C | 98 mm | 80% | 0.1 m/s | 5.6 |
| 1997 ❄️ | 17.6°C | 11.5°C | 5.5°C | 25.8°C | 0.3°C | 143 mm | 76% | 0 m/s | 5.4 |
| 1996 | 19.7°C | 14.4°C | 9.1°C | 27.8°C | -1.7°C | 150 mm | 82% | 0.1 m/s | 4.7 |
| 1995 | 20.1°C | 14.5°C | 9.0°C | 25.3°C | 1.6°C | 149 mm | 79% | 0.1 m/s | 5 |
| 1994 | 18.4°C | 12.3°C | 6.2°C | 26.2°C | 0.3°C | 79 mm | 77% | 0.1 m/s | 5.4 |
| 1993 | 21.4°C | 15.2°C | 9.0°C | 29.0°C | 3.4°C | 52 mm | 76% | 0.1 m/s | 5.2 |
| 1992 | 20.1°C | 13.9°C | 7.6°C | 26.9°C | 0.8°C | 67 mm | 76% | 0.1 m/s | 5.5 |
| 1991 | 24.4°C | 18.7°C | 13.0°C | 29.4°C | 4.5°C | 58 mm | 79% | 0.1 m/s | 5.8 |
| 1990 | 18.6°C | 13.2°C | 7.8°C | 23.5°C | 3.2°C | 154 mm | 79% | 0 m/s | 4.6 |
| 1989 | 17.7°C | 12.9°C | 8.1°C | 26.9°C | 0.9°C | 149 mm | 85% | 0 m/s | 4.3 |
| 1988 | 21.4°C | 15.1°C | 8.9°C | 29.4°C | 1.9°C | 95 mm | 76% | 0.1 m/s | 5.6 |
| 1987 | 23.1°C | 16.7°C | 10.4°C | 29.5°C | 0.7°C | 100 mm | 78% | 0.1 m/s | 6.1 |
| 1986 | 21.4°C | 15.4°C | 9.5°C | 26.9°C | -3.0°C | 61 mm | 78% | 0.1 m/s | 5.2 |
| 1985 | 21.3°C | 15.4°C | 9.4°C | 27.8°C | 1.0°C | 162 mm | 79% | 0 m/s | 5.5 |
| 1984 | 18.4°C | 13.0°C | 7.6°C | 26.0°C | -0.6°C | 129 mm | 80% | 0 m/s | 4.3 |
| 1983 | 18.8°C | 12.9°C | 7.0°C | 25.1°C | -2.2°C | 154 mm | 79% | 0.1 m/s | — |
| 1982 | 23.8°C | 17.7°C | 11.7°C | 29.1°C | 4.5°C | 85 mm | 77% | 0.1 m/s | — |
| 1981 | 19.8°C | 13.5°C | 7.3°C | 25.9°C | -1.3°C | 100 mm | 76% | 0.1 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 21.3°C with lows near 9.7°C (mean 15.5°C), based on 45 years of NASA POWER data.
May averages 106 mm of rainfall in Washington, a relatively wet time of year. The wettest on record was 172 mm in 2025.
The hottest May reached 33.3°C in 2006. The coldest dipped to -5.1°C in 2020.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.5°C. Daytime highs moved from 20.4°C to 21.9°C and overnight lows from 8.6°C to 10.2°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 21.3°C daytime highs and 9.7°C at night.
Not quite — May is the 8th coolest month in Washington, averaging 15.5°C.
For May in Washington, pack light layers you can adjust through the day, with typical highs of 21.3°C and lows of 9.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 78% — quite humid.
Average wind speed in May is 0.1 m/s. The windiest May on record averaged 0.1 m/s (1981).
The wettest May on record was 2025 with 172 mm. On average, May sees 106 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.
