May is one of the warmer months of the year in Welwyn Garden City, with average highs near 16.7°C and lows around 6.9°C (mean 11.8°C). It is about average for rainfall, averaging 55 mm of rainfall and 80% relative humidity across the period.
May is one of the warmer months of the year in Welwyn Garden City. Across 45 years of records, the warmest May in Welwyn Garden City was 1992 — when the month averaged 13.7°C — while the coldest was 1996 at 8.9°C. Typical May days reach 16.7°C with nights near 6.9°C. The long-term trend is warming, about 0.4°C per decade.
May is about average for rainfall in Welwyn Garden City, averaging 55 mm of rainfall. The wettest May on record was 2007 with 128 mm, while the driest was 2020 at 4 mm.
Relative humidity in Welwyn Garden City during May averages 80%. The most humid May was 1981 at 85%, and the least humid was 2020 at 74%.
May receives about 4.9 kWh/m²/day of solar energy in Welwyn Garden City. The sunniest May was 2020 at 6.5 kWh/m²/day, and the cloudiest were 1984 and 1986 at 4.2.
Average wind speed in Welwyn Garden City during May is 3.1 m/s. The windiest May was 1986 at 4 m/s, while the calmest was 2004 at 2.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 10.9°C | 11.7°C | 12.1°C | 11.9°C | 12.4°C | +1.5°C |
| Avg High | 15.6°C | 16.8°C | 16.8°C | 16.8°C | 17.5°C | +1.9°C |
| Avg Low | 6.3°C | 6.5°C | 7.4°C | 6.9°C | 7.3°C | +1°C |
| Avg Rain | 62 mm | 42 mm | 67 mm | 56 mm | 47 mm | -15 mm |
May temperatures in Welwyn Garden City have risen by about 1.8°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -1.2°C (1981) to a record high of 26.6°C (2005).
Rainfall in May is about average for rainfall, averaging 55 mm, with a wettest year of 128 mm.
A good time to visit Welwyn Garden City
May is a good time to visit Welwyn Garden City, with days averaging 16.7°C and nights around 6.9°C (mean 11.8°C, warmer than Welwyn Garden City's yearly average) and moderate 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 | 18.6°C | 13.1°C | 7.5°C | 24.7°C | 3.1°C | 22 mm | 76% | 3.2 m/s | 5.7 |
| 2024 | 18.4°C | 13.6°C | 8.8°C | 23.0°C | 5.6°C | 76 mm | 84% | 2.6 m/s | 4.6 |
| 2023 | 17.4°C | 12.4°C | 7.3°C | 20.3°C | 4.0°C | 45 mm | 80% | 2.9 m/s | 5.4 |
| 2022 | 18.0°C | 13.1°C | 8.1°C | 23.0°C | 3.8°C | 45 mm | 80% | 2.8 m/s | 5 |
| 2021 | 14.3°C | 10.0°C | 5.6°C | 21.4°C | 1.0°C | 88 mm | 82% | 3.3 m/s | 4.5 |
| 2020 | 18.1°C | 12.3°C | 6.5°C | 24.5°C | -0.1°C | 4 mm | 74% | 2.9 m/s | 6.5 |
| 2019 | 16.6°C | 11.6°C | 6.5°C | 22.7°C | 1.3°C | 41 mm | 77% | 2.5 m/s | 5 |
| 2018 | 19.1°C | 13.3°C | 7.4°C | 24.4°C | 1.6°C | 61 mm | 78% | 2.6 m/s | 5.4 |
| 2017 | 17.9°C | 13.2°C | 8.4°C | 23.9°C | 3.0°C | 67 mm | 80% | 3.1 m/s | 4.7 |
| 2016 | 17.2°C | 12.2°C | 7.3°C | 22.7°C | 0.3°C | 50 mm | 79% | 3.2 m/s | 5.1 |
| 2015 | 15.7°C | 11.0°C | 6.3°C | 19.8°C | 0.6°C | 61 mm | 78% | 3.6 m/s | 4.9 |
| 2014 | 16.8°C | 12.3°C | 7.8°C | 22.5°C | -0.2°C | 84 mm | 80% | 3 m/s | 4.6 |
| 2013 | 14.8°C | 10.3°C | 5.8°C | 20.0°C | 0.7°C | 64 mm | 80% | 3.3 m/s | 4.6 |
| 2012 | 17.1°C | 12.2°C | 7.4°C | 24.8°C | 1.9°C | 58 mm | 80% | 3.1 m/s | 4.6 |
| 2011 | 17.3°C | 12.2°C | 7.0°C | 20.8°C | 0.2°C | 33 mm | 75% | 3.7 m/s | 5.2 |
| 2010 | 15.4°C | 10.4°C | 5.4°C | 24.5°C | -0.1°C | 39 mm | 77% | 2.7 m/s | 4.9 |
| 2009 | 17.1°C | 12.3°C | 7.4°C | 22.3°C | 3.1°C | 44 mm | 79% | 3.5 m/s | 5.2 |
| 2008 | 18.3°C | 13.2°C | 8.0°C | 23.8°C | 2.3°C | 74 mm | 80% | 3.1 m/s | 4.6 |
| 2007 🌧️ | 16.5°C | 12.1°C | 7.7°C | 23.6°C | 2.1°C | 128 mm | 82% | 3.3 m/s | 4.4 |
| 2006 | 17.0°C | 12.4°C | 7.8°C | 24.0°C | 3.2°C | 93 mm | 80% | 3.3 m/s | 4.5 |
| 2005 | 16.0°C | 11.2°C | 6.3°C | 26.6°C | 0.7°C | 34 mm | 78% | 3.5 m/s | 4.8 |
| 2004 | 16.8°C | 12.0°C | 7.2°C | 22.3°C | 2.7°C | 53 mm | 81% | 2.2 m/s | 4.8 |
| 2003 | 16.4°C | 11.8°C | 7.2°C | 24.7°C | 2.1°C | 52 mm | 81% | 3.2 m/s | 4.6 |
| 2002 | 16.1°C | 11.9°C | 7.6°C | 22.6°C | 2.6°C | 63 mm | 82% | 3.6 m/s | 4.4 |
| 2001 | 17.2°C | 12.2°C | 7.1°C | 23.2°C | 0.6°C | 42 mm | 82% | 2.9 m/s | 4.9 |
| 2000 | 16.9°C | 12.2°C | 7.6°C | 23.9°C | 4.2°C | 88 mm | 82% | 3.1 m/s | 4.7 |
| 1999 | 17.6°C | 12.7°C | 7.8°C | 22.1°C | 5.1°C | 45 mm | 80% | 3.2 m/s | 4.5 |
| 1998 | 17.9°C | 12.8°C | 7.7°C | 24.3°C | 2.5°C | 24 mm | 81% | 2.9 m/s | 5.7 |
| 1997 | 16.7°C | 11.3°C | 6.0°C | 22.8°C | -0.1°C | 50 mm | 77% | 3 m/s | 5.2 |
| 1996 ❄️ | 13.5°C | 8.9°C | 4.2°C | 21.9°C | 0.1°C | 45 mm | 77% | 3.8 m/s | 4.3 |
| 1995 | 16.5°C | 11.2°C | 5.9°C | 23.8°C | -0.8°C | 32 mm | 78% | 2.9 m/s | 4.9 |
| 1994 | 15.0°C | 10.6°C | 6.1°C | 19.2°C | 1.9°C | 82 mm | 81% | 2.9 m/s | 4.5 |
| 1993 | 16.8°C | 11.8°C | 6.8°C | 21.6°C | 1.0°C | 51 mm | 78% | 3.7 m/s | 4.4 |
| 1992 🔥 | 19.4°C | 13.7°C | 7.9°C | 25.4°C | 2.7°C | 58 mm | 75% | 3 m/s | 5.7 |
| 1991 | 15.7°C | 10.8°C | 5.9°C | 22.3°C | 1.3°C | 21 mm | 76% | 2.9 m/s | 4.3 |
| 1990 | 18.5°C | 12.7°C | 6.8°C | 24.4°C | 2.5°C | 13 mm | 75% | 2.4 m/s | 5.5 |
| 1989 | 18.7°C | 12.9°C | 7.1°C | 25.3°C | 2.7°C | 9 mm | 78% | 2.6 m/s | 5.6 |
| 1988 | 16.6°C | 11.9°C | 7.3°C | 21.8°C | 2.5°C | 54 mm | 81% | 3 m/s | 4.7 |
| 1987 | 14.7°C | 9.8°C | 4.9°C | 20.6°C | 0.9°C | 49 mm | 79% | 3.4 m/s | 4.3 |
| 1986 | 15.4°C | 10.9°C | 6.5°C | 20.0°C | 2.6°C | 64 mm | 81% | 4 m/s | 4.2 |
| 1985 | 15.8°C | 11.3°C | 6.8°C | 22.6°C | 3.8°C | 63 mm | 82% | 3.2 m/s | 4.3 |
| 1984 | 14.1°C | 9.6°C | 5.1°C | 19.4°C | 1.0°C | 78 mm | 80% | 3 m/s | 4.2 |
| 1983 | 13.9°C | 9.8°C | 5.8°C | 18.3°C | 3.1°C | 82 mm | 84% | 3 m/s | — |
| 1982 | 16.3°C | 11.3°C | 6.3°C | 23.4°C | -0.4°C | 61 mm | 79% | 2.8 m/s | — |
| 1981 | 15.2°C | 10.9°C | 6.7°C | 21.2°C | -1.2°C | 95 mm | 85% | 3.1 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 16.7°C with lows near 6.9°C (mean 11.8°C), based on 45 years of NASA POWER data.
May averages 55 mm of rainfall in Welwyn Garden City, about average for rainfall. The wettest on record was 128 mm in 2007.
The hottest May reached 26.6°C in 2005. The coldest dipped to -1.2°C in 1981.
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 15.1°C to 17.3°C and overnight lows from 6.1°C to 7.5°C over the same span.
May is one of the warmer months of the year in Welwyn Garden City and about average for rainfall, so plan for around 16.7°C daytime highs and 6.9°C at night.
Not quite — May is the 8th coolest month in Welwyn Garden City, averaging 11.8°C.
For May in Welwyn Garden City, pack warm layers and a jacket for chilly mornings, with typical highs of 16.7°C and lows of 6.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 80% — quite humid.
Average wind speed in May is 3.1 m/s. The windiest May on record averaged 4 m/s (1986).
The wettest May on record was 2007 with 128 mm. On average, May sees 55 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 Welwyn Garden City 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.
