May is one of the warmer months of the year in New Castle, with average highs near 21.2°C and lows around 8.7°C (mean 15°C). It is a relatively wet time of year, averaging 96 mm of rainfall and 76% relative humidity across the period.
May is one of the warmer months of the year in New Castle. Across 45 years of records, the warmest May in New Castle was 2018 — when the month averaged 19°C — while the coldest was 1997 at 10.7°C. Typical May days reach 21.2°C with nights near 8.7°C. The long-term trend is warming, about 0.4°C per decade.
May is a relatively wet time of year in New Castle, averaging 96 mm of rainfall. The wettest May on record was 1995 with 177 mm, while the driest was 2023 at 36 mm.
Relative humidity in New Castle during May averages 76%. The most humid May was 2011 at 85%, and the least humid was 2023 at 68%.
May receives about 5.3 kWh/m²/day of solar energy in New Castle. The sunniest Mays were 2007 and 2023 at 6.3 kWh/m²/day, and the cloudiest was 1989 at 4.2.
Average wind speed in New Castle 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 | 14.4°C | 14.3°C | 14.6°C | 16.4°C | 15.1°C | +0.7°C |
| Avg High | 20.7°C | 20.6°C | 21.0°C | 22.6°C | 21.3°C | +0.6°C |
| Avg Low | 8.1°C | 8.0°C | 8.2°C | 10.3°C | 9.0°C | +0.9°C |
| Avg Rain | 106 mm | 90 mm | 103 mm | 91 mm | 87 mm | -20 mm |
May temperatures in New Castle have risen by about 1.4°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -4.7°C (2020) to a record high of 34.9°C (2018).
Rainfall in May is a relatively wet time of year, averaging 96 mm, with a wettest year of 177 mm.
A good time to visit New Castle
May is a good time to visit New Castle, with days averaging 21.2°C and nights around 8.7°C (mean 15°C, warmer than New Castle'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 | 20.3°C | 14.7°C | 9.1°C | 27.8°C | 1.2°C | 123 mm | 80% | 0 m/s | 4.6 |
| 2024 | 24.0°C | 17.8°C | 11.7°C | 31.0°C | 4.1°C | 97 mm | 76% | 0.1 m/s | 5.5 |
| 2023 | 21.6°C | 14.4°C | 7.3°C | 30.2°C | 0.3°C | 36 mm | 68% | 0.1 m/s | 6.3 |
| 2022 | 22.4°C | 16.5°C | 10.5°C | 30.0°C | 2.2°C | 105 mm | 78% | 0 m/s | 5.6 |
| 2021 | 20.6°C | 14.3°C | 8.0°C | 30.5°C | -2.0°C | 86 mm | 70% | 0.1 m/s | 5.5 |
| 2020 | 18.6°C | 13.1°C | 7.5°C | 29.7°C | -4.7°C | 72 mm | 78% | 0 m/s | 5.2 |
| 2019 | 22.3°C | 16.3°C | 10.3°C | 28.1°C | 3.8°C | 97 mm | 81% | 0 m/s | 4.7 |
| 2018 🔥 | 25.1°C | 19.0°C | 13.0°C | 34.9°C | 3.1°C | 83 mm | 80% | 0.1 m/s | 5.5 |
| 2017 | 20.0°C | 14.4°C | 8.7°C | 27.5°C | -1.6°C | 121 mm | 78% | 0.1 m/s | 5 |
| 2016 | 20.9°C | 15.0°C | 9.0°C | 30.6°C | -0.5°C | 60 mm | 76% | 0.1 m/s | 5.5 |
| 2015 | 24.5°C | 17.8°C | 11.1°C | 31.2°C | 1.6°C | 83 mm | 73% | 0.1 m/s | 5.6 |
| 2014 | 21.3°C | 15.1°C | 8.9°C | 27.9°C | -0.5°C | 96 mm | 77% | 0.1 m/s | 5.3 |
| 2013 | 22.1°C | 15.7°C | 9.3°C | 29.6°C | -0.8°C | 45 mm | 74% | 0 m/s | 5.9 |
| 2012 | 25.4°C | 18.5°C | 11.6°C | 32.7°C | 2.3°C | 71 mm | 74% | 0.1 m/s | 6 |
| 2011 | 20.9°C | 15.7°C | 10.5°C | 30.1°C | -0.1°C | 137 mm | 85% | 0 m/s | 4.8 |
| 2010 | 23.0°C | 16.6°C | 10.2°C | 32.0°C | -0.4°C | 114 mm | 76% | 0.1 m/s | 5.4 |
| 2009 | 21.3°C | 15.1°C | 8.8°C | 28.7°C | 0.1°C | 75 mm | 73% | 0.1 m/s | 5.8 |
| 2008 | 18.6°C | 12.5°C | 6.4°C | 26.6°C | 2.2°C | 84 mm | 77% | 0.1 m/s | 5 |
| 2007 | 23.7°C | 16.2°C | 8.7°C | 32.4°C | 2.2°C | 51 mm | 72% | 0.1 m/s | 6.3 |
| 2006 | 20.4°C | 14.2°C | 7.9°C | 34.4°C | -0.3°C | 120 mm | 76% | 0.1 m/s | 5.3 |
| 2005 | 18.9°C | 12.6°C | 6.4°C | 26.0°C | -1.7°C | 72 mm | 75% | 0.1 m/s | 5.7 |
| 2004 | 23.3°C | 17.1°C | 10.8°C | 29.2°C | -2.3°C | 160 mm | 81% | 0 m/s | 5 |
| 2003 | 20.0°C | 14.3°C | 8.5°C | 25.0°C | 3.6°C | 164 mm | 80% | 0 m/s | 4.6 |
| 2002 | 19.4°C | 12.6°C | 5.9°C | 26.5°C | -1.9°C | 120 mm | 75% | 0.1 m/s | 5 |
| 2001 | 21.9°C | 15.3°C | 8.8°C | 30.2°C | 2.1°C | 79 mm | 72% | 0.1 m/s | 5.1 |
| 2000 | 22.5°C | 16.1°C | 9.7°C | 28.9°C | 3.0°C | 104 mm | 74% | 0 m/s | 4.8 |
| 1999 | 23.5°C | 16.2°C | 8.8°C | 31.4°C | 5.1°C | 59 mm | 68% | 0.1 m/s | 5.9 |
| 1998 | 23.4°C | 17.3°C | 11.2°C | 34.1°C | 4.9°C | 65 mm | 77% | 0.1 m/s | 5.8 |
| 1997 ❄️ | 16.6°C | 10.7°C | 4.8°C | 25.3°C | -0.3°C | 131 mm | 77% | 0 m/s | 5.2 |
| 1996 | 19.2°C | 13.5°C | 7.7°C | 28.0°C | -1.7°C | 110 mm | 80% | 0.1 m/s | 4.8 |
| 1995 🌧️ | 19.6°C | 13.7°C | 7.8°C | 25.5°C | 0.5°C | 177 mm | 77% | 0.1 m/s | 5.1 |
| 1994 | 18.6°C | 12.1°C | 5.5°C | 28.3°C | -0.3°C | 60 mm | 74% | 0.1 m/s | 5.2 |
| 1993 | 21.3°C | 14.5°C | 7.8°C | 30.9°C | 2.9°C | 47 mm | 74% | 0.1 m/s | 5 |
| 1992 | 20.6°C | 13.6°C | 6.6°C | 29.6°C | 0.6°C | 55 mm | 73% | 0.1 m/s | 5.5 |
| 1991 | 24.9°C | 18.7°C | 12.5°C | 30.7°C | 2.9°C | 61 mm | 76% | 0.1 m/s | 5.7 |
| 1990 | 18.4°C | 12.7°C | 7.0°C | 24.0°C | 1.4°C | 134 mm | 78% | 0 m/s | 4.8 |
| 1989 | 17.6°C | 12.7°C | 7.7°C | 26.2°C | 0.6°C | 168 mm | 82% | 0 m/s | 4.2 |
| 1988 | 22.3°C | 15.1°C | 8.0°C | 31.3°C | 1.5°C | 64 mm | 71% | 0.1 m/s | 5.9 |
| 1987 | 23.0°C | 16.1°C | 9.3°C | 29.8°C | -0.1°C | 75 mm | 76% | 0.1 m/s | 6 |
| 1986 | 21.3°C | 15.1°C | 8.9°C | 27.9°C | -3.2°C | 80 mm | 77% | 0.1 m/s | 5 |
| 1985 | 21.4°C | 14.9°C | 8.4°C | 28.8°C | 0.9°C | 128 mm | 76% | 0 m/s | 5.6 |
| 1984 | 18.0°C | 12.3°C | 6.6°C | 26.1°C | -0.3°C | 141 mm | 79% | 0 m/s | 4.3 |
| 1983 | 18.4°C | 12.1°C | 5.8°C | 24.6°C | -4.6°C | 127 mm | 78% | 0.1 m/s | — |
| 1982 | 24.2°C | 17.7°C | 11.1°C | 30.0°C | 3.8°C | 88 mm | 75% | 0.1 m/s | — |
| 1981 | 19.7°C | 13.4°C | 7.1°C | 27.0°C | -2.3°C | 86 mm | 73% | 0.1 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 21.2°C with lows near 8.7°C (mean 15°C), based on 45 years of NASA POWER data.
May averages 96 mm of rainfall in New Castle, a relatively wet time of year. The wettest on record was 177 mm in 1995.
The hottest May reached 34.9°C in 2018. The coldest dipped to -4.7°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 20.3°C to 21.8°C and overnight lows from 7.8°C to 9.3°C over the same span.
May is one of the warmer months of the year in New Castle and a relatively wet time of year, so plan for around 21.2°C daytime highs and 8.7°C at night.
Not quite — May is the 8th coolest month in New Castle, averaging 15°C.
For May in New Castle, pack light layers you can adjust through the day, with typical highs of 21.2°C and lows of 8.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 76% — 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 1995 with 177 mm. On average, May sees 96 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 New Castle 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.
