January is one of the cooler months of the year in Santa Rosa, with average highs near 12.9°C and lows around 3.6°C (mean 8.3°C). It is a relatively wet time of year, averaging 137 mm of rainfall and 84% relative humidity across the period.
January is one of the cooler months of the year in Santa Rosa. Across 45 years of records, the warmest January in Santa Rosa was 2014 — when the month averaged 11.4°C — while the coldest was 1982 at 5.3°C. Typical January days reach 12.9°C with nights near 3.6°C. The long-term trend is warming, about 0.2°C per decade.
January is a relatively wet time of year in Santa Rosa, averaging 137 mm of rainfall. The wettest January on record was 1995 with 497 mm, while the driest was 2015 at 2 mm.
Relative humidity in Santa Rosa during January averages 84%. The most humid January was 1998 at 94%, and the least humid was 2014 at 56%.
January receives about 2.3 kWh/m²/day of solar energy in Santa Rosa. The sunniest January was 2007 at 2.9 kWh/m²/day, and the cloudiest were 1995 and 1998 at 1.6.
Average wind speed in Santa Rosa during January is 1.5 m/s. The windiest Januarys were 1995 and 2023 at 2.1 m/s, while the calmest was 2003 at 1.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 7.8°C | 8.4°C | 7.8°C | 8.6°C | 8.9°C | +1.1°C |
| Avg High | 12.6°C | 12.9°C | 12.4°C | 13.3°C | 13.5°C | +0.9°C |
| Avg Low | 2.9°C | 3.9°C | 3.2°C | 3.9°C | 4.2°C | +1.3°C |
| Avg Rain | 124 mm | 193 mm | 114 mm | 136 mm | 104 mm | -20 mm |
January temperatures in Santa Rosa have risen by about 1.3°C between 1981–1985 and 2021–2025.
January has ranged from a record low of -4.3°C (1997) to a record high of 23°C (2014).
Rainfall in January is a relatively wet time of year, averaging 137 mm, with a wettest year of 497 mm.
A quieter season to visit Santa Rosa
If your dates are flexible, the more temperate months of September and July tend to be the most comfortable for visiting Santa Rosa. That said, January — with days averaging 12.9°C and nights around 3.6°C (mean 8.3°C) and higher rainfall (137 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 | 13.9°C | 8.7°C | 3.5°C | 17.2°C | -0.6°C | 21 mm | 83% | 1.5 m/s | 2.8 |
| 2024 | 13.6°C | 9.5°C | 5.4°C | 19.7°C | -0.8°C | 166 mm | 91% | 1.4 m/s | 2 |
| 2023 | 11.8°C | 7.8°C | 3.8°C | 15.8°C | -2.3°C | 285 mm | 87% | 2.1 m/s | 2.2 |
| 2022 | 14.5°C | 9.1°C | 3.7°C | 17.3°C | -2.6°C | 11 mm | 85% | 1.4 m/s | 2.8 |
| 2021 | 14.2°C | 9.5°C | 4.7°C | 23.0°C | -1.2°C | 86 mm | 79% | 1.4 m/s | 2.4 |
| 2020 | 13.0°C | 8.5°C | 4.1°C | 19.4°C | 0.9°C | 55 mm | 90% | 1.3 m/s | 2.3 |
| 2019 | 13.3°C | 9.4°C | 5.4°C | 17.7°C | -0.9°C | 192 mm | 86% | 1.6 m/s | 2.1 |
| 2018 | 13.8°C | 9.6°C | 5.4°C | 19.0°C | 0.5°C | 137 mm | 88% | 1.2 m/s | 2.1 |
| 2017 | 10.8°C | 6.6°C | 2.5°C | 14.8°C | -3.7°C | 374 mm | 90% | 1.9 m/s | 2.2 |
| 2016 | 11.9°C | 8.5°C | 5.1°C | 15.7°C | -2.6°C | 207 mm | 90% | 1.5 m/s | 1.8 |
| 2015 | 14.7°C | 9.8°C | 4.8°C | 17.9°C | -1.0°C | 2 mm | 85% | 1.2 m/s | 2.7 |
| 2014 🔥 | 18.0°C | 11.4°C | 4.8°C | 23.0°C | 2.3°C | 3 mm | 56% | 1.4 m/s | 2.8 |
| 2013 | 11.7°C | 6.3°C | 0.8°C | 17.4°C | -3.6°C | 23 mm | 85% | 1.4 m/s | 2.8 |
| 2012 | 14.7°C | 8.8°C | 3.0°C | 20.4°C | -2.9°C | 123 mm | 74% | 1.5 m/s | 2.6 |
| 2011 | 12.7°C | 7.8°C | 2.9°C | 18.9°C | -1.7°C | 43 mm | 86% | 1.4 m/s | 2.5 |
| 2010 | 11.6°C | 8.2°C | 4.7°C | 15.4°C | 1.3°C | 262 mm | 91% | 1.6 m/s | 1.7 |
| 2009 | 15.1°C | 9.1°C | 3.1°C | 20.9°C | -3.1°C | 21 mm | 73% | 1.5 m/s | 2.7 |
| 2008 | 9.8°C | 6.2°C | 2.6°C | 13.8°C | -0.6°C | 297 mm | 89% | 1.9 m/s | 1.9 |
| 2007 | 12.4°C | 6.8°C | 1.2°C | 16.8°C | -3.6°C | 9 mm | 76% | 1.5 m/s | 2.9 |
| 2006 | 11.7°C | 7.7°C | 3.7°C | 14.8°C | -0.4°C | 125 mm | 91% | 1.5 m/s | 2.2 |
| 2005 | 11.7°C | 7.5°C | 3.3°C | 16.6°C | -1.8°C | 131 mm | 89% | 1.5 m/s | 2.1 |
| 2004 | 11.8°C | 7.5°C | 3.3°C | 14.9°C | -2.0°C | 87 mm | 90% | 1.3 m/s | 2.1 |
| 2003 | 14.8°C | 10.8°C | 6.9°C | 20.2°C | 2.9°C | 89 mm | 90% | 1.1 m/s | 2 |
| 2002 | 11.2°C | 6.5°C | 1.9°C | 15.2°C | -2.6°C | 92 mm | 86% | 1.3 m/s | 2.5 |
| 2001 | 12.5°C | 7.3°C | 2.1°C | 19.0°C | -1.9°C | 122 mm | 78% | 1.6 m/s | 2.5 |
| 2000 | 12.5°C | 8.4°C | 4.3°C | 16.0°C | -1.1°C | 165 mm | 88% | 1.4 m/s | 2 |
| 1999 | 13.2°C | 8.1°C | 3.0°C | 16.7°C | -2.1°C | 93 mm | 82% | 1.6 m/s | 2.3 |
| 1998 | 11.9°C | 9.0°C | 6.1°C | 16.7°C | -1.3°C | 273 mm | 94% | 1.5 m/s | 1.6 |
| 1997 | 12.2°C | 8.2°C | 4.2°C | 16.8°C | -4.3°C | 220 mm | 87% | 1.5 m/s | 2 |
| 1996 | 13.0°C | 8.7°C | 4.3°C | 17.4°C | -0.6°C | 203 mm | 87% | 1.6 m/s | 2 |
| 1995 🌧️ | 11.4°C | 9.0°C | 6.5°C | 18.1°C | 0.8°C | 497 mm | 94% | 2.1 m/s | 1.6 |
| 1994 | 14.0°C | 8.8°C | 3.6°C | 18.4°C | -0.7°C | 76 mm | 81% | 1.4 m/s | 2.5 |
| 1993 | 10.7°C | 6.5°C | 2.2°C | 14.9°C | -2.9°C | 306 mm | 87% | 1.8 m/s | 2.2 |
| 1992 | 13.3°C | 8.1°C | 2.9°C | 16.6°C | -0.3°C | 96 mm | 81% | 1.4 m/s | 2.4 |
| 1991 | 15.4°C | 9.0°C | 2.7°C | 21.7°C | -1.7°C | 19 mm | 69% | 1.4 m/s | 2.6 |
| 1990 | 13.4°C | 8.2°C | 3.1°C | 16.9°C | -1.5°C | 144 mm | 82% | 1.6 m/s | 2.5 |
| 1989 | 12.5°C | 6.9°C | 1.3°C | 17.6°C | -2.5°C | 34 mm | 81% | 1.6 m/s | 2.7 |
| 1988 | 11.5°C | 7.5°C | 3.4°C | 16.9°C | -2.2°C | 167 mm | 87% | 1.6 m/s | 2.1 |
| 1987 | 12.3°C | 7.3°C | 2.2°C | 18.9°C | -2.8°C | 98 mm | 77% | 1.6 m/s | 2.4 |
| 1986 | 14.2°C | 10.1°C | 6.0°C | 18.0°C | 2.2°C | 174 mm | 84% | 1.4 m/s | 1.9 |
| 1985 | 12.7°C | 7.0°C | 1.4°C | 17.2°C | -2.6°C | 26 mm | 81% | 1.3 m/s | 2.5 |
| 1984 | 13.2°C | 8.1°C | 2.9°C | 18.5°C | -2.7°C | 14 mm | 86% | 1.4 m/s | 2.5 |
| 1983 | 12.9°C | 8.3°C | 3.8°C | 16.6°C | -2.3°C | 230 mm | 85% | 1.7 m/s | — |
| 1982 ❄️ | 9.9°C | 5.3°C | 0.7°C | 15.1°C | -3.8°C | 195 mm | 87% | 1.8 m/s | — |
| 1981 | 14.1°C | 9.4°C | 4.6°C | 19.0°C | -1.4°C | 175 mm | 81% | 1.5 m/s | — |
Actual recorded January data for each year, 1981–2025 — sourced from NASA POWER.
The average high in January is around 12.9°C with lows near 3.6°C (mean 8.3°C), based on 45 years of NASA POWER data.
January averages 137 mm of rainfall in Santa Rosa, a relatively wet time of year. The wettest on record was 497 mm in 1995.
The hottest January reached 23°C in 2014. The coldest dipped to -4.3°C in 1997.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average January temperatures have risen by about 1.3°C. Daytime highs moved from 12.6°C to 13.6°C and overnight lows from 2.7°C to 4.2°C over the same span.
January is one of the cooler months of the year in Santa Rosa and a relatively wet time of year, so plan for around 12.9°C daytime highs and 3.6°C at night.
Yes — January is the coldest month of the year in Santa Rosa, averaging 8.3°C.
For January in Santa Rosa, pack warm layers and a jacket for chilly mornings, with typical highs of 12.9°C and lows of 3.6°C. Bring an umbrella or light rain jacket too.
Relative humidity in January averages 84% — quite humid.
Average wind speed in January is 1.5 m/s. The windiest January on record averaged 2.1 m/s (1995).
The wettest January on record was 1995 with 497 mm. On average, January sees 137 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 Santa Rosa behaves each January, 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 January specifically, along with year-by-year records and how the month has changed over the decades.
