May is one of the warmer months of the year in Watertown, with average highs near 17.5°C and lows around 6.7°C (mean 12.1°C). It is about average for rainfall, averaging 90 mm of rainfall and 79% relative humidity across the period.
May is one of the warmer months of the year in Watertown. Across 45 years of records, the warmest May in Watertown was 2024 — when the month averaged 15.1°C — while the coldest was 1997 at 8.5°C. Typical May days reach 17.5°C with nights near 6.7°C. The long-term trend is warming, about 0.4°C per decade.
May is about average for rainfall in Watertown, averaging 90 mm of rainfall. The wettest May on record was 2003 with 155 mm, while the driest was 2005 at 29 mm.
Relative humidity in Watertown during May averages 79%. The most humid May was 2011 at 85%, and the least humid was 2023 at 72%.
May receives about 5.3 kWh/m²/day of solar energy in Watertown. The sunniest May was 2023 at 6.4 kWh/m²/day, and the cloudiest was 1984 at 4.
Average wind speed in Watertown during May is 0.2 m/s. The windiest Mays were 2020, 2021 and 2023, among others at 0.3 m/s, while the calmest were 2022, 2024 and 2025, among others at 0.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 11.7°C | 11.4°C | 11.6°C | 13.2°C | 12.7°C | +1°C |
| Avg High | 17.0°C | 16.9°C | 17.0°C | 18.7°C | 18.2°C | +1.2°C |
| Avg Low | 6.5°C | 5.9°C | 6.3°C | 7.7°C | 7.3°C | +0.8°C |
| Avg Rain | 89 mm | 91 mm | 101 mm | 92 mm | 70 mm | -18 mm |
May temperatures in Watertown have risen by about 1.9°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -3.3°C (2020) to a record high of 29.5°C (2020).
Rainfall in May is about average for rainfall, averaging 90 mm, with a wettest year of 155 mm.
A good time to visit Watertown
May is a good time to visit Watertown, with days averaging 17.5°C and nights around 6.7°C (mean 12.1°C, warmer than Watertown's yearly average) and higher rainfall. July and August 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 | 16.6°C | 12.0°C | 7.4°C | 24.4°C | 0.9°C | 113 mm | 83% | 0.2 m/s | 4.3 |
| 2024 🔥 | 20.1°C | 15.1°C | 10.1°C | 28.6°C | 5.3°C | 83 mm | 80% | 0.2 m/s | 5.4 |
| 2023 | 17.6°C | 11.5°C | 5.4°C | 28.5°C | -1.0°C | 44 mm | 72% | 0.3 m/s | 6.4 |
| 2022 | 20.5°C | 14.4°C | 8.4°C | 27.5°C | 0.3°C | 81 mm | 77% | 0.2 m/s | 5.8 |
| 2021 | 17.8°C | 12.2°C | 6.6°C | 27.3°C | -2.4°C | 40 mm | 74% | 0.3 m/s | 5.9 |
| 2020 | 16.4°C | 11.0°C | 5.6°C | 29.5°C | -3.3°C | 59 mm | 77% | 0.3 m/s | 5.8 |
| 2019 | 15.8°C | 10.7°C | 5.6°C | 21.6°C | 2.4°C | 139 mm | 82% | 0.2 m/s | 4.6 |
| 2018 | 20.1°C | 14.2°C | 8.4°C | 28.1°C | 0.7°C | 43 mm | 78% | 0.2 m/s | 5.8 |
| 2017 | 16.4°C | 11.5°C | 6.7°C | 26.2°C | -1.3°C | 135 mm | 81% | 0.3 m/s | 4.5 |
| 2016 | 17.8°C | 12.4°C | 7.0°C | 27.7°C | 0.6°C | 45 mm | 77% | 0.3 m/s | 6 |
| 2015 | 20.4°C | 14.4°C | 8.4°C | 27.4°C | -1.7°C | 69 mm | 74% | 0.3 m/s | 6 |
| 2014 | 17.7°C | 12.4°C | 7.0°C | 24.8°C | -0.2°C | 108 mm | 81% | 0.2 m/s | 5.6 |
| 2013 | 19.3°C | 13.7°C | 8.0°C | 28.0°C | -0.5°C | 88 mm | 76% | 0.3 m/s | 5.6 |
| 2012 | 20.4°C | 14.9°C | 9.4°C | 27.3°C | 1.7°C | 77 mm | 79% | 0.2 m/s | 5.7 |
| 2011 | 18.7°C | 13.6°C | 8.5°C | 27.8°C | 0.5°C | 148 mm | 85% | 0.2 m/s | 4.7 |
| 2010 | 20.1°C | 14.1°C | 8.1°C | 29.0°C | -2.8°C | 63 mm | 75% | 0.2 m/s | 5.7 |
| 2009 | 16.8°C | 11.5°C | 6.2°C | 22.9°C | 1.1°C | 132 mm | 78% | 0.3 m/s | 5.3 |
| 2008 | 15.5°C | 10.2°C | 4.9°C | 21.3°C | -0.6°C | 65 mm | 78% | 0.3 m/s | 5.7 |
| 2007 | 18.1°C | 11.9°C | 5.8°C | 26.0°C | -0.1°C | 48 mm | 75% | 0.2 m/s | 6.1 |
| 2006 | 17.7°C | 12.6°C | 7.5°C | 28.0°C | 0.0°C | 66 mm | 80% | 0.2 m/s | 5 |
| 2005 | 15.7°C | 10.3°C | 4.9°C | 24.1°C | -2.0°C | 29 mm | 76% | 0.2 m/s | 5.6 |
| 2004 | 18.4°C | 13.1°C | 7.8°C | 27.5°C | -0.6°C | 151 mm | 82% | 0.2 m/s | 5 |
| 2003 🌧️ | 16.8°C | 11.7°C | 6.7°C | 23.5°C | -0.8°C | 155 mm | 81% | 0.2 m/s | 4.7 |
| 2002 | 14.6°C | 9.5°C | 4.4°C | 25.8°C | -2.0°C | 147 mm | 78% | 0.3 m/s | 5.1 |
| 2001 | 18.7°C | 13.1°C | 7.6°C | 24.9°C | 1.5°C | 69 mm | 78% | 0.2 m/s | 5.7 |
| 2000 | 17.6°C | 12.4°C | 7.3°C | 24.8°C | 0.8°C | 144 mm | 82% | 0.2 m/s | 4.6 |
| 1999 | 19.9°C | 13.7°C | 7.5°C | 27.1°C | 0.1°C | 52 mm | 74% | 0.2 m/s | 6.1 |
| 1998 | 20.2°C | 14.8°C | 9.4°C | 26.5°C | 3.5°C | 63 mm | 79% | 0.2 m/s | 5.7 |
| 1997 ❄️ | 13.5°C | 8.5°C | 3.5°C | 21.5°C | -3.0°C | 80 mm | 80% | 0.3 m/s | 4.7 |
| 1996 | 15.0°C | 9.7°C | 4.5°C | 24.0°C | -1.7°C | 118 mm | 78% | 0.2 m/s | 5.8 |
| 1995 | 16.4°C | 11.1°C | 5.7°C | 20.8°C | -2.8°C | 55 mm | 77% | 0.3 m/s | 5.4 |
| 1994 | 15.5°C | 9.9°C | 4.4°C | 24.8°C | -1.2°C | 86 mm | 80% | 0.2 m/s | 5.1 |
| 1993 | 16.7°C | 11.4°C | 6.1°C | 24.0°C | 0.3°C | 79 mm | 79% | 0.2 m/s | 5.1 |
| 1992 | 17.5°C | 11.3°C | 5.2°C | 24.1°C | -1.5°C | 125 mm | 77% | 0.2 m/s | 5.8 |
| 1991 | 19.4°C | 13.9°C | 8.3°C | 25.8°C | 1.4°C | 103 mm | 80% | 0.2 m/s | 5.4 |
| 1990 | 14.8°C | 9.8°C | 4.8°C | 22.4°C | -1.0°C | 144 mm | 81% | 0.3 m/s | 4.6 |
| 1989 | 16.6°C | 12.0°C | 7.3°C | 25.9°C | 0.2°C | 119 mm | 82% | 0.2 m/s | 4.5 |
| 1988 | 18.4°C | 12.7°C | 7.0°C | 24.7°C | 0.0°C | 67 mm | 78% | 0.2 m/s | 5.5 |
| 1987 | 18.1°C | 12.4°C | 6.7°C | 26.9°C | -1.7°C | 52 mm | 77% | 0.2 m/s | 5.2 |
| 1986 | 18.2°C | 13.2°C | 8.3°C | 24.8°C | -2.7°C | 90 mm | 80% | 0.2 m/s | 5.4 |
| 1985 | 17.6°C | 12.1°C | 6.6°C | 24.8°C | -2.0°C | 78 mm | 77% | 0.2 m/s | 5.5 |
| 1984 | 14.1°C | 9.3°C | 4.6°C | 23.9°C | -2.0°C | 130 mm | 82% | 0.3 m/s | 4 |
| 1983 | 14.5°C | 9.5°C | 4.5°C | 22.7°C | -3.0°C | 109 mm | 81% | 0.3 m/s | — |
| 1982 | 18.4°C | 12.9°C | 7.5°C | 25.8°C | 1.7°C | 80 mm | 80% | 0.2 m/s | — |
| 1981 | 17.5°C | 11.6°C | 5.8°C | 24.3°C | -2.9°C | 73 mm | 77% | 0.3 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 17.5°C with lows near 6.7°C (mean 12.1°C), based on 45 years of NASA POWER data.
May averages 90 mm of rainfall in Watertown, about average for rainfall. The wettest on record was 155 mm in 2003.
The hottest May reached 29.5°C in 2020. The coldest dipped to -3.3°C in 2020.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.9°C. Daytime highs moved from 16.4°C to 18.5°C and overnight lows from 5.8°C to 7.6°C over the same span.
May is one of the warmer months of the year in Watertown and about average for rainfall, so plan for around 17.5°C daytime highs and 6.7°C at night.
Not quite — May is the 8th coolest month in Watertown, averaging 12.1°C.
For May in Watertown, pack warm layers and a jacket for chilly mornings, with typical highs of 17.5°C and lows of 6.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 79% — quite humid.
Average wind speed in May is 0.2 m/s. The windiest May on record averaged 0.3 m/s (1981).
The wettest May on record was 2003 with 155 mm. On average, May sees 90 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 Watertown 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.
