May is one of the warmer months of the year in Belfast, with average highs near 12.7°C and lows around 7.9°C (mean 10.3°C). It is one of the drier months, averaging 65 mm of rainfall and 85% relative humidity across the period.
May is one of the warmer months of the year in Belfast. Across 45 years of records, the warmest May in Belfast was 2024 — when the month averaged 12.4°C — while the coldest was 1996 at 8.3°C. Typical May days reach 12.7°C with nights near 7.9°C. The long-term trend is warming, about 0.3°C per decade.
May is one of the drier months in Belfast, averaging 65 mm of rainfall. The wettest May on record was 2003 with 127 mm, while the driest was 1991 at 15 mm.
Relative humidity in Belfast during May averages 85%. The most humid May was 2024 at 88%, and the least humid was 1984 at 80%.
May receives about 5 kWh/m²/day of solar energy in Belfast. The sunniest May was 2025 at 6.1 kWh/m²/day, and the cloudiest were 1986 and 1993 at 4.
Average wind speed in Belfast during May is 4.1 m/s. The windiest May was 2011 at 6.1 m/s, while the calmest was 1990 at 2.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 9.7°C | 10.1°C | 10.5°C | 10.2°C | 11.2°C | +1.5°C |
| Avg High | 12.0°C | 12.5°C | 12.9°C | 12.6°C | 13.6°C | +1.6°C |
| Avg Low | 7.4°C | 7.7°C | 8.1°C | 7.8°C | 8.8°C | +1.4°C |
| Avg Rain | 60 mm | 59 mm | 80 mm | 65 mm | 61 mm | +2 mm |
May temperatures in Belfast have risen by about 1.8°C between 1981–1985 and 2021–2025.
May has ranged from a record low of 1.4°C (1982) to a record high of 20.1°C (1990).
Rainfall in May is one of the drier months, averaging 65 mm, with a wettest year of 127 mm.
A good time to visit Belfast
May is a good time to visit Belfast, with days averaging 12.7°C and nights around 7.9°C (mean 10.3°C, close to Belfast'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 | 14.8°C | 12.0°C | 9.1°C | 17.9°C | 5.5°C | 41 mm | 81% | 3.3 m/s | 6.1 |
| 2024 🔥 | 14.6°C | 12.4°C | 10.1°C | 17.0°C | 7.3°C | 72 mm | 88% | 3.4 m/s | 4.5 |
| 2023 | 14.0°C | 11.5°C | 8.9°C | 17.3°C | 6.9°C | 34 mm | 86% | 3.1 m/s | 5.3 |
| 2022 | 13.5°C | 11.3°C | 9.0°C | 14.9°C | 7.0°C | 82 mm | 87% | 4.3 m/s | 4.6 |
| 2021 | 11.7°C | 9.5°C | 7.2°C | 16.7°C | 2.6°C | 110 mm | 84% | 4 m/s | 5.2 |
| 2020 | 13.2°C | 10.7°C | 8.2°C | 17.2°C | 3.7°C | 29 mm | 82% | 3.8 m/s | 5.6 |
| 2019 | 12.4°C | 10.0°C | 7.7°C | 15.9°C | 4.3°C | 44 mm | 83% | 3.5 m/s | 4.9 |
| 2018 | 13.8°C | 11.1°C | 8.4°C | 19.2°C | 4.9°C | 47 mm | 86% | 3.6 m/s | 5.2 |
| 2017 | 14.2°C | 11.4°C | 8.6°C | 18.3°C | 5.6°C | 48 mm | 85% | 3.6 m/s | 5.5 |
| 2016 | 13.4°C | 10.8°C | 8.1°C | 17.0°C | 5.2°C | 54 mm | 85% | 4 m/s | 5.2 |
| 2015 | 11.2°C | 9.0°C | 6.8°C | 14.0°C | 4.9°C | 110 mm | 85% | 5.2 m/s | 4.7 |
| 2014 | 13.0°C | 10.9°C | 8.8°C | 17.5°C | 6.0°C | 86 mm | 87% | 3.6 m/s | 4.2 |
| 2013 | 11.6°C | 9.1°C | 6.7°C | 14.4°C | 4.4°C | 88 mm | 85% | 4.9 m/s | 4.8 |
| 2012 | 12.4°C | 9.9°C | 7.5°C | 18.6°C | 3.5°C | 60 mm | 84% | 3.6 m/s | 5.2 |
| 2011 | 12.3°C | 10.3°C | 8.3°C | 14.1°C | 5.9°C | 80 mm | 84% | 6.1 m/s | 4.6 |
| 2010 | 12.0°C | 9.6°C | 7.2°C | 19.9°C | 4.0°C | 34 mm | 83% | 3.6 m/s | 5.4 |
| 2009 | 12.6°C | 10.3°C | 8.0°C | 17.3°C | 5.1°C | 87 mm | 86% | 4.8 m/s | 4.8 |
| 2008 | 14.0°C | 11.6°C | 9.3°C | 18.8°C | 5.8°C | 36 mm | 84% | 3.8 m/s | 5.3 |
| 2007 | 12.8°C | 10.4°C | 8.1°C | 16.9°C | 6.1°C | 58 mm | 84% | 4.1 m/s | 5.4 |
| 2006 | 12.4°C | 10.0°C | 7.6°C | 18.6°C | 4.6°C | 108 mm | 85% | 4.6 m/s | 4.8 |
| 2005 | 11.9°C | 9.7°C | 7.5°C | 14.4°C | 4.9°C | 102 mm | 84% | 4.5 m/s | 5.1 |
| 2004 | 13.2°C | 10.7°C | 8.2°C | 16.5°C | 6.3°C | 48 mm | 86% | 3.3 m/s | 5.4 |
| 2003 🌧️ | 12.2°C | 10.1°C | 8.0°C | 18.3°C | 5.0°C | 127 mm | 87% | 4.8 m/s | 4.4 |
| 2002 | 12.7°C | 10.5°C | 8.3°C | 14.8°C | 5.6°C | 112 mm | 86% | 4.8 m/s | 4.5 |
| 2001 | 13.7°C | 11.0°C | 8.4°C | 18.1°C | 5.0°C | 56 mm | 84% | 3.1 m/s | 5.3 |
| 2000 | 13.1°C | 10.4°C | 7.7°C | 17.5°C | 5.4°C | 67 mm | 84% | 3.8 m/s | 5.9 |
| 1999 | 13.1°C | 10.8°C | 8.5°C | 15.7°C | 6.5°C | 61 mm | 86% | 4.2 m/s | 4.8 |
| 1998 | 13.4°C | 11.0°C | 8.6°C | 18.1°C | 5.8°C | 42 mm | 87% | 4 m/s | 5.3 |
| 1997 | 12.6°C | 10.2°C | 7.8°C | 18.6°C | 2.1°C | 92 mm | 84% | 3.9 m/s | 5 |
| 1996 ❄️ | 10.7°C | 8.3°C | 5.9°C | 15.8°C | 2.7°C | 76 mm | 82% | 4.2 m/s | 4.7 |
| 1995 | 11.7°C | 9.6°C | 7.5°C | 16.7°C | 3.4°C | 56 mm | 85% | 4.5 m/s | 4.6 |
| 1994 | 11.5°C | 9.2°C | 6.8°C | 15.8°C | 4.4°C | 39 mm | 82% | 4.6 m/s | 5 |
| 1993 | 12.1°C | 9.7°C | 7.3°C | 15.6°C | 3.5°C | 125 mm | 85% | 4.6 m/s | 4 |
| 1992 | 13.4°C | 10.8°C | 8.2°C | 17.5°C | 3.3°C | 41 mm | 86% | 4.8 m/s | 5 |
| 1991 | 12.7°C | 10.2°C | 7.7°C | 16.7°C | 4.9°C | 15 mm | 85% | 3.7 m/s | 4.8 |
| 1990 | 13.8°C | 11.3°C | 8.8°C | 20.1°C | 6.5°C | 43 mm | 83% | 2.8 m/s | 5.1 |
| 1989 | 13.2°C | 10.5°C | 7.8°C | 18.4°C | 4.7°C | 30 mm | 84% | 3.8 m/s | 5.2 |
| 1988 | 12.7°C | 10.3°C | 7.9°C | 17.8°C | 5.1°C | 52 mm | 85% | 3.9 m/s | 4.8 |
| 1987 | 11.8°C | 9.4°C | 6.9°C | 15.1°C | 4.4°C | 35 mm | 84% | 4.4 m/s | 4.6 |
| 1986 | 11.2°C | 9.2°C | 7.3°C | 13.7°C | 4.2°C | 109 mm | 87% | 5.8 m/s | 4 |
| 1985 | 11.7°C | 9.4°C | 7.1°C | 15.0°C | 3.8°C | 65 mm | 84% | 3.8 m/s | 4.4 |
| 1984 | 12.2°C | 9.5°C | 6.9°C | 15.7°C | 4.9°C | 27 mm | 80% | 3.5 m/s | 5.4 |
| 1983 | 11.1°C | 9.1°C | 7.1°C | 13.8°C | 4.9°C | 72 mm | 85% | 4.3 m/s | — |
| 1982 | 11.9°C | 9.5°C | 7.1°C | 16.3°C | 1.4°C | 41 mm | 84% | 4.2 m/s | — |
| 1981 | 12.2°C | 10.2°C | 8.1°C | 17.1°C | 4.2°C | 106 mm | 87% | 4.3 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 12.7°C with lows near 7.9°C (mean 10.3°C), based on 45 years of NASA POWER data.
May averages 65 mm of rainfall in Belfast, one of the drier months. The wettest on record was 127 mm in 2003.
The hottest May reached 20.1°C in 1990. The coldest dipped to 1.4°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 11.8°C to 13.7°C and overnight lows from 7.3°C to 8.9°C over the same span.
May is one of the warmer months of the year in Belfast and one of the drier months, so plan for around 12.7°C daytime highs and 7.9°C at night.
Not quite — May is the 7th coolest month in Belfast, averaging 10.3°C.
For May in Belfast, pack warm layers and a jacket for chilly mornings, with typical highs of 12.7°C and lows of 7.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 85% — quite humid.
Average wind speed in May is 4.1 m/s. The windiest May on record averaged 6.1 m/s (2011).
The wettest May on record was 2003 with 127 mm. On average, May sees 65 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 Belfast 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.
