December is one of the cooler months of the year in New Castle, with average highs near 6.6°C and lows around -1.5°C (mean 2.6°C). It is about average for rainfall, averaging 96 mm of rainfall and 84% relative humidity across the period.
December is one of the cooler months of the year in New Castle. Across 45 years of records, the warmest December in New Castle was 2015 — when the month averaged 9.1°C — while the coldest was 1989 at -4.6°C. Typical December days reach 6.6°C with nights near -1.5°C. The long-term trend is warming, about 0.5°C per decade.
December is about average for rainfall in New Castle, averaging 96 mm of rainfall. The wettest December on record was 2023 with 213 mm, while the driest was 1988 at 24 mm.
Relative humidity in New Castle during December averages 84%. The most humid December was 1996 at 90%, and the least humid was 1998 at 75%.
December receives about 1.8 kWh/m²/day of solar energy in New Castle. The sunniest Decembers were 2000, 2001 and 2006, among others at 2 kWh/m²/day, and the cloudiest were 1992 and 2014 at 1.4.
Average wind speed in New Castle during December is 2.8 m/s. The windiest December was 2010 at 3.5 m/s, while the calmest were 2021 and 2023 at 2.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 1.2°C | 2.9°C | 2.2°C | 3.5°C | 3.3°C | +2.1°C |
| Avg High | 5.2°C | 7.0°C | 6.2°C | 7.4°C | 7.5°C | +2.3°C |
| Avg Low | -2.8°C | -1.3°C | -1.9°C | -0.4°C | -1.0°C | +1.8°C |
| Avg Rain | 78 mm | 97 mm | 102 mm | 101 mm | 106 mm | +28 mm |
December temperatures in New Castle have risen by about 1.5°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -17.6°C (1989) to a record high of 23.3°C (1998).
Rainfall in December is about average for rainfall, averaging 96 mm, with a wettest year of 213 mm.
A quieter season to visit New Castle
If your dates are flexible, the more temperate months of June and September tend to be the most comfortable for visiting New Castle. That said, December — with days averaging 6.6°C and nights around -1.5°C (mean 2.6°C) and higher rainfall (96 mm) — can still be rewarding for travellers who don't mind the cooler conditions, and often means fewer crowds.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 4.4°C | 0.5°C | -3.4°C | 14.1°C | -9.3°C | 71 mm | 79% | 3 m/s | — |
| 2024 | 7.4°C | 3.1°C | -1.3°C | 17.4°C | -8.8°C | 80 mm | 79% | 2.7 m/s | 1.9 |
| 2023 🌧️ | 9.4°C | 5.2°C | 1.0°C | 15.9°C | -3.6°C | 213 mm | 88% | 2.3 m/s | 1.6 |
| 2022 | 6.8°C | 2.3°C | -2.2°C | 15.3°C | -13.7°C | 124 mm | 85% | 2.7 m/s | 1.9 |
| 2021 | 10.3°C | 5.9°C | 1.4°C | 17.2°C | -5.5°C | 26 mm | 81% | 2.3 m/s | 1.8 |
| 2020 | 6.6°C | 2.6°C | -1.5°C | 16.6°C | -7.2°C | 121 mm | 87% | 2.9 m/s | 1.8 |
| 2019 | 7.2°C | 3.2°C | -0.7°C | 14.9°C | -7.9°C | 117 mm | 85% | 2.5 m/s | 1.6 |
| 2018 | 7.4°C | 3.6°C | -0.3°C | 16.2°C | -5.3°C | 151 mm | 89% | 2.5 m/s | 1.7 |
| 2017 | 5.1°C | 1.2°C | -2.6°C | 16.3°C | -11.8°C | 32 mm | 78% | 2.6 m/s | 1.8 |
| 2016 | 6.5°C | 2.4°C | -1.6°C | 16.9°C | -9.1°C | 77 mm | 79% | 2.8 m/s | 1.7 |
| 2015 🔥 | 13.1°C | 9.1°C | 5.2°C | 20.6°C | -3.2°C | 131 mm | 88% | 2.5 m/s | 1.5 |
| 2014 | 7.4°C | 3.6°C | -0.3°C | 16.5°C | -4.0°C | 91 mm | 86% | 2.7 m/s | 1.4 |
| 2013 | 6.4°C | 2.4°C | -1.6°C | 19.6°C | -9.8°C | 128 mm | 88% | 2.5 m/s | 1.6 |
| 2012 | 8.9°C | 5.0°C | 1.1°C | 18.8°C | -3.5°C | 110 mm | 87% | 2.7 m/s | 1.6 |
| 2011 | 9.3°C | 4.9°C | 0.5°C | 16.2°C | -4.2°C | 105 mm | 87% | 2.5 m/s | 1.9 |
| 2010 | 2.5°C | -0.8°C | -4.0°C | 16.7°C | -8.2°C | 63 mm | 80% | 3.5 m/s | 1.9 |
| 2009 | 4.7°C | 1.0°C | -2.8°C | 17.9°C | -12.0°C | 195 mm | 87% | 3.2 m/s | 1.9 |
| 2008 | 6.5°C | 2.4°C | -1.6°C | 16.8°C | -9.5°C | 122 mm | 84% | 3.1 m/s | 1.7 |
| 2007 | 6.0°C | 2.5°C | -1.1°C | 14.8°C | -6.6°C | 121 mm | 85% | 2.7 m/s | 1.5 |
| 2006 | 9.8°C | 5.3°C | 0.8°C | 21.1°C | -5.0°C | 52 mm | 84% | 2.6 m/s | 2 |
| 2005 | 4.5°C | 0.5°C | -3.4°C | 10.2°C | -12.0°C | 77 mm | 85% | 2.7 m/s | 1.9 |
| 2004 | 7.0°C | 2.7°C | -1.6°C | 15.5°C | -11.2°C | 72 mm | 84% | 3 m/s | 1.9 |
| 2003 | 5.6°C | 1.7°C | -2.3°C | 13.6°C | -8.7°C | 135 mm | 86% | 3.4 m/s | 1.9 |
| 2002 | 4.2°C | 0.6°C | -3.1°C | 14.5°C | -10.3°C | 123 mm | 87% | 3 m/s | 1.8 |
| 2001 | 10.4°C | 5.7°C | 1.1°C | 21.2°C | -7.6°C | 47 mm | 76% | 2.7 m/s | 2 |
| 2000 | 3.2°C | -0.8°C | -4.9°C | 17.5°C | -12.0°C | 79 mm | 76% | 3 m/s | 2 |
| 1999 | 7.7°C | 3.4°C | -0.9°C | 16.9°C | -7.0°C | 72 mm | 83% | 2.8 m/s | 1.9 |
| 1998 | 9.7°C | 5.3°C | 0.9°C | 23.3°C | -7.2°C | 41 mm | 75% | 2.5 m/s | 1.7 |
| 1997 | 6.7°C | 2.7°C | -1.4°C | 12.6°C | -6.3°C | 67 mm | 84% | 2.8 m/s | 2 |
| 1996 | 7.3°C | 3.7°C | 0.2°C | 14.4°C | -7.8°C | 193 mm | 90% | 3 m/s | 1.6 |
| 1995 | 1.9°C | -1.9°C | -5.7°C | 12.8°C | -11.9°C | 64 mm | 88% | 3 m/s | 2 |
| 1994 | 8.5°C | 4.1°C | -0.3°C | 17.3°C | -5.5°C | 55 mm | 84% | 2.7 m/s | 1.7 |
| 1993 | 5.4°C | 1.4°C | -2.6°C | 15.0°C | -9.2°C | 123 mm | 85% | 3 m/s | 1.6 |
| 1992 | 6.2°C | 2.3°C | -1.5°C | 16.2°C | -9.1°C | 109 mm | 85% | 3.1 m/s | 1.4 |
| 1991 | 7.4°C | 3.2°C | -1.0°C | 20.1°C | -8.5°C | 114 mm | 83% | 2.9 m/s | 1.8 |
| 1990 | 9.2°C | 4.5°C | -0.3°C | 18.1°C | -6.4°C | 128 mm | 84% | 3.2 m/s | 1.6 |
| 1989 ❄️ | -0.5°C | -4.6°C | -8.7°C | 9.8°C | -17.6°C | 44 mm | 85% | 2.9 m/s | 1.9 |
| 1988 | 4.8°C | 0.6°C | -3.6°C | 15.9°C | -12.6°C | 24 mm | 80% | 2.8 m/s | 1.8 |
| 1987 | 6.9°C | 3.0°C | -0.9°C | 14.6°C | -8.9°C | 60 mm | 83% | 3 m/s | 1.7 |
| 1986 | 6.5°C | 2.5°C | -1.5°C | 14.3°C | -5.7°C | 162 mm | 87% | 2.6 m/s | 1.8 |
| 1985 | 4.1°C | 0.2°C | -3.7°C | 11.9°C | -11.8°C | 25 mm | 81% | 3 m/s | 2 |
| 1984 | 9.2°C | 5.0°C | 0.8°C | 18.7°C | -4.8°C | 47 mm | 86% | 2.5 m/s | 1.7 |
| 1983 | 3.4°C | -0.4°C | -4.2°C | 14.4°C | -16.8°C | 179 mm | 86% | 3.2 m/s | — |
| 1982 | 8.6°C | 4.5°C | 0.4°C | 20.9°C | -8.1°C | 59 mm | 87% | 2.7 m/s | — |
| 1981 | 3.6°C | 0.0°C | -3.6°C | 13.1°C | -13.3°C | 104 mm | 86% | 3 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 6.6°C with lows near -1.5°C (mean 2.6°C), based on 45 years of NASA POWER data.
December averages 96 mm of rainfall in New Castle, about average for rainfall. The wettest on record was 213 mm in 2023.
The hottest December reached 23.3°C in 1998. The coldest dipped to -17.6°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.5°C. Daytime highs moved from 5.8°C to 7.7°C and overnight lows from -2.1°C to -0.9°C over the same span.
December is one of the cooler months of the year in New Castle and about average for rainfall, so plan for around 6.6°C daytime highs and -1.5°C at night.
Not quite — December is the 3rd coolest month in New Castle, averaging 2.6°C.
For December in New Castle, pack warm layers and a jacket for chilly mornings, with typical highs of 6.6°C and lows of -1.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 84% — quite humid.
Average wind speed in December is 2.8 m/s. The windiest December on record averaged 3.5 m/s (2010).
The wettest December on record was 2023 with 213 mm. On average, December 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 December, 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 December specifically, along with year-by-year records and how the month has changed over the decades.
