December is one of the cooler months of the year in Siwan, with average highs near 27.7°C and lows around 6.1°C (mean 16.9°C). It is one of the drier months, averaging 6 mm of rainfall and 53% relative humidity across the period.
December is one of the cooler months of the year in Siwan. Across 45 years of records, the warmest December in Siwan was 2023 — when the month averaged 20.2°C — while the coldest was 2007 at 13.8°C. Typical December days reach 27.7°C with nights near 6.1°C. The long-term trend is cooling, about 0.2°C per decade.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 17.3°C | 17.2°C | 16.7°C | 16.6°C | 16.7°C | -0.6°C |
| Avg High | 27.9°C | 28.2°C | 27.0°C | 27.8°C | 27.6°C | -0.3°C |
| Avg Low | 6.8°C | 6.2°C | 6.3°C | 5.4°C | 5.8°C | -1°C |
| Avg Rain | 10 mm | 8 mm | 2 mm | 4 mm | 4 mm | -6 mm |
December temperatures in Siwan have stayed relatively stable across the record.
December has ranged from a record low of 1.9°C (2019) to a record high of 31.9°C (2015).
Rainfall in December is one of the drier months, averaging 6 mm, with a wettest year of 36 mm.
A good time to visit Siwan
December is a good time to visit Siwan, with days averaging 27.7°C and nights around 6.1°C (mean 16.9°C, cooler than Siwan's yearly average) and low rainfall. November and February are marginally more temperate, but December still suits most travellers.
| Year | High | Low | Avg | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|
| 2025 | 24.1°C | 6.1°C | 15.1°C | 0 mm | 77% | 1.4 m/s | — |
| 2024 | 28.7°C | 5.2°C | 16.9°C | 0 mm | 56% | 1.5 m/s | 2.9 |
| 2023 🔥 | 31.9°C | 8.4°C | 20.2°C | 6 mm | 57% | 1.5 m/s | 2.7 |
| 2022 | 27.6°C | 6.8°C | 17.2°C | 0 mm | 65% | 1.6 m/s | 2.9 |
| 2021 | 26.4°C | 3.7°C | 15.0°C | 14 mm | 79% | 1.6 m/s | 2.9 |
| 2020 | 27.0°C | 4.3°C | 15.6°C | 2 mm | 59% | 1.6 m/s | 2.6 |
| 2019 | 26.1°C | 1.9°C | 14.0°C | 26 mm | 75% | 1.6 m/s | 2.3 |
| 2018 | 28.3°C | 4.6°C | 16.5°C | 1 mm | 46% | 1.5 m/s | 2.9 |
| 2017 | 30.3°C | 8.0°C | 19.2°C | 0 mm | 47% | 1.4 m/s | 2.7 |
| 2016 | 27.4°C | 6.7°C | 17.1°C | 0 mm | 62% | 1.5 m/s | 2.2 |
| 2015 | 31.9°C | 6.6°C | 19.2°C | 1 mm | 37% | 1.3 m/s | 2.6 |
| 2014 | 26.6°C | 4.3°C | 15.4°C | 7 mm | 58% | 1.6 m/s | 2.3 |
| 2013 | 25.8°C | 7.0°C | 16.4°C | 0 mm | 64% | 1.4 m/s | 2.8 |
| 2012 | 25.8°C | 3.9°C | 14.8°C | 0 mm | 58% | 1.7 m/s | 2.5 |
| 2011 | 27.8°C | 5.4°C | 16.6°C | 0 mm | 56% | 1.1 m/s | 2.3 |
| 2010 | 28.2°C | 5.3°C | 16.7°C | 1 mm | 56% | 1.3 m/s | 3.3 |
| 2009 | 27.8°C | 5.5°C | 16.6°C | 4 mm | 53% | 1.5 m/s | 3.2 |
| 2008 | 26.2°C | 7.9°C | 17.0°C | 0 mm | 75% | 1.1 m/s | 2.4 |
| 2007 ❄️ | 23.8°C | 3.7°C | 13.8°C | 0 mm | 68% | 1.3 m/s | 3.2 |
| 2006 | 28.9°C | 7.3°C | 18.1°C | 3 mm | 52% | 1.3 m/s | 3.3 |
| 2005 | 27.9°C | 6.0°C | 17.0°C | 0 mm | 51% | 1.3 m/s | 3.4 |
| 2004 | 28.2°C | 5.4°C | 16.8°C | 0 mm | 50% | 1.2 m/s | 2.8 |
| 2003 | 28.7°C | 6.1°C | 17.4°C | 6 mm | 55% | 1.2 m/s | 3.2 |
| 2002 | 27.5°C | 7.9°C | 17.7°C | 10 mm | 43% | 1.3 m/s | 2.9 |
| 2001 | 24.9°C | 6.2°C | 15.5°C | 0 mm | 54% | 1.1 m/s | 2.6 |
| 2000 | 26.4°C | 6.7°C | 16.6°C | 0 mm | 42% | 1.2 m/s | 3.8 |
| 1999 | 29.4°C | 7.0°C | 18.2°C | 0 mm | 39% | 1.2 m/s | 3.5 |
| 1998 | 26.1°C | 6.7°C | 16.4°C | 0 mm | 52% | 1.1 m/s | 3.4 |
| 1997 🌧️ | 28.0°C | 5.1°C | 16.6°C | 36 mm | 67% | 1.5 m/s | 2.5 |
| 1996 | 27.0°C | 3.8°C | 15.4°C | 0 mm | 43% | 1.4 m/s | 3.8 |
| 1995 | 28.1°C | 6.7°C | 17.4°C | 31 mm | 48% | 1.5 m/s | 3.5 |
| 1994 | 30.0°C | 5.0°C | 17.5°C | 0 mm | 34% | 1.5 m/s | 4 |
| 1993 | 27.6°C | 6.3°C | 16.9°C | 0 mm | 39% | 1.2 m/s | 3.6 |
| 1992 | 28.9°C | 8.3°C | 18.6°C | 1 mm | 36% | 1.3 m/s | 3.8 |
| 1991 | 28.3°C | 6.5°C | 17.4°C | 14 mm | 45% | 1.5 m/s | 3.4 |
| 1990 | 28.3°C | 6.2°C | 17.2°C | 0 mm | 44% | 1.4 m/s | 3.7 |
| 1989 | 29.0°C | 7.0°C | 18.0°C | 11 mm | 37% | 1.2 m/s | 3.6 |
| 1988 | 28.6°C | 8.5°C | 18.5°C | 25 mm | 43% | 1.3 m/s | 3.7 |
| 1987 | 25.7°C | 6.2°C | 16.0°C | 2 mm | 62% | 1.1 m/s | 3.7 |
| 1986 | 28.4°C | 7.4°C | 17.9°C | 24 mm | 48% | 1.4 m/s | 3.5 |
| 1985 | 25.9°C | 6.4°C | 16.1°C | 4 mm | 73% | 1.6 m/s | 3.8 |
| 1984 | 28.9°C | 3.8°C | 16.4°C | 2 mm | 40% | 1.6 m/s | 3.6 |
| 1983 | 29.5°C | 7.2°C | 18.3°C | 8 mm | 39% | 1.6 m/s | — |
| 1982 | 29.2°C | 7.5°C | 18.3°C | 3 mm | 45% | 1.9 m/s | — |
| 1981 | 25.8°C | 6.8°C | 16.3°C | 13 mm | 59% | 1.5 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 27.7°C with lows near 6.1°C (mean 16.9°C), based on 45 years of NASA POWER data.
December averages 6 mm of rainfall in Siwan, one of the drier months. The wettest on record was 36 mm in 1997.
The hottest December reached 31.9°C in 2015. The coldest dipped to 1.9°C in 2019.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have fallen by about 0.2°C. Daytime highs moved from 27.9°C to 27.7°C and overnight lows from 6.3°C to 6°C over the same span.
December is one of the cooler months of the year in Siwan and one of the drier months, so plan for around 27.7°C daytime highs and 6.1°C at night.
Not quite — December is the 2nd coolest month in Siwan, averaging 16.9°C.
For December in Siwan, pack warm layers and a jacket for chilly mornings, with typical highs of 27.7°C and lows of 6.1°C.
Relative humidity in December averages 53% — relatively dry.
Average wind speed in December is 1.4 m/s. The windiest December on record averaged 1.9 m/s (1982).
The wettest December on record was 1997 with 36 mm. On average, December sees 6 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 Siwan 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.
