December is one of the warmer months of the year in Horsham, with average highs near 29.1°C and lows around 12.2°C (mean 20.7°C). It is about average for rainfall, averaging 32 mm of rainfall and 49% relative humidity across the period.
December is one of the warmer months of the year in Horsham. Across 45 years of records, the warmest December in Horsham was 2015 — when the month averaged 24°C — while the coldest were 1986 and 2001 at 17.7°C. Typical December days reach 29.1°C with nights near 12.2°C. The long-term trend is warming, about 0.2°C per decade.
December is about average for rainfall in Horsham, averaging 32 mm of rainfall. The wettest December on record was 2010 with 120 mm, while the driest was 1994 at 2 mm.
Relative humidity in Horsham during December averages 49%. The most humid December was 1992 at 67%, and the least humid was 2015 at 34%.
December receives about 7.7 kWh/m²/day of solar energy in Horsham. The sunniest Decembers were 1994 and 2021 at 8.6 kWh/m²/day, and the cloudiest was 1992 at 6.3.
Average wind speed in Horsham during December is 3.6 m/s. The windiest Decembers were 1984 and 2005 at 4.2 m/s, while the calmest were 2009 and 2018 at 3.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 20.3°C | 20.4°C | 20.7°C | 21.6°C | 20.1°C | -0.2°C |
| Avg High | 28.6°C | 28.8°C | 29.3°C | 30.0°C | 28.5°C | -0.1°C |
| Avg Low | 11.9°C | 12.0°C | 12.2°C | 13.2°C | 11.7°C | -0.2°C |
| Avg Rain | 33 mm | 28 mm | 32 mm | 35 mm | 36 mm | +4 mm |
December temperatures in Horsham have stayed relatively stable across the record.
December has ranged from a record low of 5°C (1987) to a record high of 46.4°C (2019).
Rainfall in December is about average for rainfall, averaging 32 mm, with a wettest year of 120 mm.
One of the best times to visit Horsham
December is one of the best times to visit Horsham. Expect days averaging 29.1°C and nights around 12.2°C (mean 20.7°C) — warmer than Horsham's yearly average — with moderate rainfall (32 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 29.0°C | 20.1°C | 11.2°C | 40.7°C | 6.8°C | 28 mm | 49% | 3.4 m/s | — |
| 2024 | 30.3°C | 21.5°C | 12.8°C | 43.2°C | 9.3°C | 32 mm | 50% | 3.5 m/s | 8.1 |
| 2023 | 28.0°C | 20.4°C | 12.7°C | 39.5°C | 8.6°C | 95 mm | 60% | 3.6 m/s | 6.8 |
| 2022 | 27.0°C | 19.0°C | 11.1°C | 39.3°C | 5.8°C | 19 mm | 58% | 3.3 m/s | 7.9 |
| 2021 | 29.8°C | 20.7°C | 11.6°C | 38.9°C | 7.5°C | 10 mm | 49% | 3.5 m/s | 8.6 |
| 2020 | 26.9°C | 18.7°C | 10.5°C | 35.9°C | 7.0°C | 34 mm | 53% | 3.8 m/s | 7.7 |
| 2019 | 32.5°C | 23.2°C | 13.8°C | 46.4°C | 7.4°C | 9 mm | 42% | 3.9 m/s | 8.4 |
| 2018 | 30.6°C | 22.6°C | 14.6°C | 41.0°C | 9.5°C | 67 mm | 53% | 3.2 m/s | 7.2 |
| 2017 | 28.9°C | 20.9°C | 12.9°C | 39.6°C | 6.8°C | 31 mm | 52% | 3.4 m/s | 7.4 |
| 2016 | 30.1°C | 21.5°C | 12.8°C | 39.1°C | 7.3°C | 26 mm | 46% | 3.5 m/s | 7.9 |
| 2015 🔥 | 32.9°C | 24.0°C | 15.1°C | 42.7°C | 7.0°C | 13 mm | 34% | 3.5 m/s | 8.1 |
| 2014 | 30.0°C | 21.8°C | 13.5°C | 36.5°C | 9.2°C | 11 mm | 43% | 3.4 m/s | 7.9 |
| 2013 | 30.4°C | 21.4°C | 12.3°C | 42.6°C | 5.6°C | 11 mm | 45% | 3.5 m/s | 7.6 |
| 2012 | 29.8°C | 21.3°C | 12.8°C | 39.5°C | 8.9°C | 13 mm | 44% | 3.7 m/s | 7.7 |
| 2011 | 29.4°C | 20.9°C | 12.5°C | 36.9°C | 6.9°C | 48 mm | 51% | 3.3 m/s | 8.2 |
| 2010 🌧️ | 25.2°C | 18.4°C | 11.6°C | 40.1°C | 6.5°C | 120 mm | 66% | 3.5 m/s | 7.2 |
| 2009 | 29.0°C | 20.2°C | 11.4°C | 38.7°C | 7.2°C | 36 mm | 52% | 3.2 m/s | 8.1 |
| 2008 | 26.6°C | 18.8°C | 11.0°C | 33.4°C | 7.4°C | 63 mm | 56% | 3.7 m/s | 7.4 |
| 2007 | 30.0°C | 21.6°C | 13.2°C | 42.8°C | 6.7°C | 43 mm | 49% | 3.4 m/s | 7.7 |
| 2006 | 30.2°C | 21.0°C | 11.9°C | 42.1°C | 6.7°C | 16 mm | 37% | 3.7 m/s | 8.4 |
| 2005 | 29.8°C | 21.1°C | 12.5°C | 45.2°C | 7.9°C | 26 mm | 47% | 4.2 m/s | 7.5 |
| 2004 | 28.9°C | 20.8°C | 12.7°C | 40.0°C | 7.6°C | 34 mm | 52% | 3.6 m/s | 7.7 |
| 2003 | 31.8°C | 23.1°C | 14.4°C | 40.6°C | 8.4°C | 34 mm | 45% | 3.5 m/s | 7.7 |
| 2002 | 30.6°C | 21.5°C | 12.4°C | 41.0°C | 5.7°C | 32 mm | 45% | 4 m/s | 7.9 |
| 2001 | 25.6°C | 17.7°C | 9.8°C | 36.9°C | 6.0°C | 14 mm | 56% | 3.7 m/s | 7.3 |
| 2000 | 30.8°C | 21.5°C | 12.3°C | 39.8°C | 7.3°C | 19 mm | 43% | 3.5 m/s | 8.3 |
| 1999 | 28.3°C | 20.2°C | 12.0°C | 37.6°C | 6.8°C | 46 mm | 51% | 3.7 m/s | 7.8 |
| 1998 | 30.3°C | 21.4°C | 12.6°C | 42.3°C | 7.5°C | 17 mm | 47% | 3.5 m/s | 7.9 |
| 1997 | 30.4°C | 21.6°C | 12.9°C | 37.6°C | 8.9°C | 5 mm | 44% | 3.6 m/s | 8 |
| 1996 | 28.0°C | 19.2°C | 10.4°C | 37.4°C | 6.6°C | 13 mm | 46% | 3.6 m/s | 7.6 |
| 1995 | 27.3°C | 18.7°C | 10.0°C | 35.5°C | 5.3°C | 16 mm | 50% | 3.8 m/s | 7.4 |
| 1994 | 32.5°C | 23.0°C | 13.5°C | 39.8°C | 5.8°C | 2 mm | 35% | 3.6 m/s | 8.6 |
| 1993 | 26.6°C | 18.7°C | 10.7°C | 34.0°C | 5.3°C | 50 mm | 56% | 3.8 m/s | 7.6 |
| 1992 | 26.1°C | 19.5°C | 13.0°C | 33.8°C | 8.0°C | 90 mm | 67% | 3.4 m/s | 6.3 |
| 1991 | 27.7°C | 19.6°C | 11.5°C | 39.4°C | 5.5°C | 25 mm | 52% | 3.6 m/s | 7.5 |
| 1990 | 30.9°C | 22.0°C | 13.1°C | 41.6°C | 7.2°C | 16 mm | 45% | 3.9 m/s | 7.7 |
| 1989 | 30.0°C | 21.3°C | 12.5°C | 38.3°C | 7.3°C | 9 mm | 45% | 3.7 m/s | 7.6 |
| 1988 | 30.2°C | 21.8°C | 13.5°C | 37.9°C | 7.7°C | 32 mm | 52% | 3.5 m/s | 7.6 |
| 1987 | 28.1°C | 19.6°C | 11.1°C | 39.6°C | 5.0°C | 66 mm | 52% | 3.6 m/s | 7.8 |
| 1986 ❄️ | 25.5°C | 17.7°C | 9.9°C | 37.1°C | 5.6°C | 60 mm | 57% | 3.8 m/s | 7.1 |
| 1985 | 26.2°C | 18.9°C | 11.6°C | 34.3°C | 8.4°C | 67 mm | 59% | 3.9 m/s | 7 |
| 1984 | 28.3°C | 19.7°C | 11.2°C | 36.9°C | 6.1°C | 8 mm | 47% | 4.2 m/s | 7.8 |
| 1983 | 29.6°C | 21.0°C | 12.3°C | 40.4°C | 6.5°C | 34 mm | 50% | 3.5 m/s | — |
| 1982 | 30.4°C | 21.8°C | 13.2°C | 38.4°C | 8.1°C | 8 mm | 40% | 3.6 m/s | — |
| 1981 | 29.2°C | 20.5°C | 11.9°C | 40.0°C | 7.2°C | 8 mm | 46% | 3.8 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 29.1°C with lows near 12.2°C (mean 20.7°C), based on 45 years of NASA POWER data.
December averages 32 mm of rainfall in Horsham, about average for rainfall. The wettest on record was 120 mm in 2010.
The hottest December reached 46.4°C in 2019. The coldest dipped to 5°C in 1987.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have fallen by about 0.1°C — but days and nights have moved in opposite directions. Daytime highs rose from 28.7°C to 28.8°C while overnight lows fell from 12°C to 11.9°C, widening the gap between day and night.
December is one of the warmer months of the year in Horsham and about average for rainfall, so plan for around 29.1°C daytime highs and 12.2°C at night.
Not quite — December is the 10th coolest month in Horsham, averaging 20.7°C.
For December in Horsham, pack light layers you can adjust through the day, with typical highs of 29.1°C and lows of 12.2°C.
Relative humidity in December averages 49% — relatively dry.
Average wind speed in December is 3.6 m/s. The windiest December on record averaged 4.2 m/s (1984).
The wettest December on record was 2010 with 120 mm. On average, December sees 32 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 Horsham 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.
