January is one of the cooler months of the year in Sunnyvale, with average highs near 14°C and lows around 4.2°C (mean 9.1°C). It is a relatively wet time of year, averaging 105 mm of rainfall and 83% relative humidity across the period.
January is one of the cooler months of the year in Sunnyvale. Across 45 years of records, the warmest January in Sunnyvale was 2014 — when the month averaged 12°C — while the coldest was 1982 at 5.8°C. Typical January days reach 14°C with nights near 4.2°C. The long-term trend is warming, about 0.2°C per decade.
January is a relatively wet time of year in Sunnyvale, averaging 105 mm of rainfall. The wettest January on record was 2017 with 309 mm, while the driest was 2015 at 0 mm.
Relative humidity in Sunnyvale during January averages 83%. The most humid January was 1998 at 91%, and the least humid was 2014 at 62%.
January receives about 2.4 kWh/m²/day of solar energy in Sunnyvale. The sunniest Januarys were 2007 and 2013 at 2.9 kWh/m²/day, and the cloudiest was 1995 at 1.9.
Average wind speed in Sunnyvale during January is 1.7 m/s. The windiest January was 1995 at 2.8 m/s, while the calmest was 2015 at 1.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 8.6°C | 9.2°C | 8.6°C | 9.6°C | 9.5°C | +0.9°C |
| Avg High | 13.8°C | 14.1°C | 13.5°C | 14.6°C | 14.3°C | +0.5°C |
| Avg Low | 3.5°C | 4.3°C | 3.7°C | 4.6°C | 4.8°C | +1.3°C |
| Avg Rain | 94 mm | 144 mm | 82 mm | 105 mm | 97 mm | +2 mm |
January temperatures in Sunnyvale have risen by about 1.2°C between 1981–1985 and 2021–2025.
January has ranged from a record low of -5.2°C (1993) to a record high of 23.4°C (1994).
Rainfall in January is a relatively wet time of year, averaging 105 mm, with a wettest year of 309 mm.
A quieter season to visit Sunnyvale
If your dates are flexible, the more temperate months of August and July tend to be the most comfortable for visiting Sunnyvale. That said, January — with days averaging 14°C and nights around 4.2°C (mean 9.1°C) and higher rainfall (105 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 | 14.8°C | 9.3°C | 3.9°C | 18.8°C | 1.0°C | 8 mm | 81% | 1.4 m/s | 2.8 |
| 2024 | 14.4°C | 10.3°C | 6.2°C | 21.7°C | 0.7°C | 155 mm | 90% | 1.7 m/s | 2.2 |
| 2023 | 12.4°C | 8.3°C | 4.2°C | 17.0°C | -2.1°C | 255 mm | 87% | 2.3 m/s | 2.4 |
| 2022 | 15.1°C | 9.8°C | 4.6°C | 17.9°C | -1.6°C | 7 mm | 85% | 1.3 m/s | 2.7 |
| 2021 | 15.3°C | 10.2°C | 5.0°C | 21.7°C | 0.3°C | 114 mm | 80% | 1.7 m/s | 2.5 |
| 2020 | 13.8°C | 9.3°C | 4.7°C | 19.4°C | 1.9°C | 42 mm | 90% | 1.5 m/s | 2.4 |
| 2019 | 14.9°C | 10.3°C | 5.8°C | 19.4°C | -3.2°C | 147 mm | 84% | 1.9 m/s | 2.2 |
| 2018 | 15.6°C | 10.9°C | 6.2°C | 19.9°C | 1.6°C | 116 mm | 88% | 1.4 m/s | 2.2 |
| 2017 🌧️ | 11.6°C | 7.6°C | 3.7°C | 18.1°C | -2.1°C | 309 mm | 90% | 2.1 m/s | 2.4 |
| 2016 | 13.9°C | 10.0°C | 6.0°C | 18.3°C | -2.6°C | 174 mm | 88% | 1.7 m/s | 2 |
| 2015 | 15.7°C | 10.4°C | 5.1°C | 19.3°C | -2.3°C | 0 mm | 85% | 1.1 m/s | 2.8 |
| 2014 🔥 | 18.6°C | 12.0°C | 5.4°C | 23.1°C | 1.0°C | 3 mm | 62% | 1.4 m/s | 2.8 |
| 2013 | 12.6°C | 7.1°C | 1.5°C | 18.7°C | -3.9°C | 19 mm | 83% | 1.4 m/s | 2.9 |
| 2012 | 15.6°C | 9.6°C | 3.6°C | 21.7°C | -1.9°C | 77 mm | 74% | 1.7 m/s | 2.6 |
| 2011 | 13.6°C | 8.6°C | 3.7°C | 19.2°C | -2.4°C | 34 mm | 87% | 1.5 m/s | 2.5 |
| 2010 | 13.5°C | 9.4°C | 5.3°C | 19.1°C | 1.9°C | 168 mm | 90% | 1.8 m/s | 2 |
| 2009 | 15.3°C | 9.1°C | 2.9°C | 21.4°C | -3.1°C | 38 mm | 75% | 1.5 m/s | 2.7 |
| 2008 | 11.5°C | 7.4°C | 3.2°C | 17.8°C | -1.5°C | 210 mm | 87% | 2.2 m/s | 2 |
| 2007 | 13.2°C | 7.1°C | 1.1°C | 18.8°C | -5.1°C | 15 mm | 74% | 1.7 m/s | 2.9 |
| 2006 | 13.3°C | 8.7°C | 4.1°C | 17.7°C | -0.5°C | 81 mm | 89% | 1.7 m/s | 2.5 |
| 2005 | 13.1°C | 8.5°C | 3.9°C | 19.1°C | -1.2°C | 96 mm | 89% | 1.7 m/s | 2.4 |
| 2004 | 13.0°C | 8.7°C | 4.5°C | 17.8°C | -2.1°C | 61 mm | 88% | 1.5 m/s | 2.2 |
| 2003 | 16.0°C | 11.4°C | 6.8°C | 18.6°C | 2.4°C | 26 mm | 89% | 1.3 m/s | 2.3 |
| 2002 | 11.8°C | 7.3°C | 2.7°C | 17.2°C | -3.6°C | 45 mm | 87% | 1.4 m/s | 2.6 |
| 2001 | 13.5°C | 8.0°C | 2.4°C | 21.7°C | -3.2°C | 101 mm | 78% | 1.8 m/s | 2.6 |
| 2000 | 13.8°C | 9.7°C | 5.7°C | 15.9°C | 0.3°C | 143 mm | 86% | 1.7 m/s | 2.1 |
| 1999 | 13.5°C | 8.5°C | 3.4°C | 18.3°C | -1.8°C | 130 mm | 82% | 1.8 m/s | 2.4 |
| 1998 | 13.5°C | 10.0°C | 6.5°C | 17.8°C | 2.3°C | 217 mm | 91% | 1.9 m/s | 2 |
| 1997 | 13.0°C | 9.1°C | 5.1°C | 17.0°C | -4.6°C | 207 mm | 90% | 1.9 m/s | 2.2 |
| 1996 | 14.1°C | 9.6°C | 5.1°C | 19.1°C | 1.1°C | 161 mm | 86% | 1.8 m/s | 2.2 |
| 1995 | 13.1°C | 10.1°C | 7.1°C | 20.0°C | 2.1°C | 263 mm | 90% | 2.8 m/s | 1.9 |
| 1994 | 15.7°C | 9.6°C | 3.5°C | 23.4°C | -1.9°C | 49 mm | 78% | 1.5 m/s | 2.7 |
| 1993 | 12.5°C | 7.8°C | 3.0°C | 17.9°C | -5.2°C | 236 mm | 86% | 2.1 m/s | 2.3 |
| 1992 | 14.6°C | 8.8°C | 2.9°C | 19.0°C | -1.9°C | 90 mm | 80% | 1.6 m/s | 2.7 |
| 1991 | 16.0°C | 9.5°C | 3.1°C | 20.8°C | -1.7°C | 9 mm | 72% | 1.4 m/s | 2.5 |
| 1990 | 14.5°C | 9.1°C | 3.7°C | 20.1°C | -0.3°C | 77 mm | 81% | 1.9 m/s | 2.7 |
| 1989 | 13.4°C | 7.6°C | 1.8°C | 19.4°C | -3.0°C | 34 mm | 80% | 1.6 m/s | 2.7 |
| 1988 | 13.6°C | 8.9°C | 4.1°C | 20.6°C | -1.0°C | 84 mm | 82% | 1.7 m/s | 2.2 |
| 1987 | 13.4°C | 7.9°C | 2.5°C | 19.1°C | -3.7°C | 70 mm | 75% | 1.8 m/s | 2.5 |
| 1986 | 15.8°C | 11.2°C | 6.6°C | 21.3°C | 2.3°C | 102 mm | 81% | 1.8 m/s | 2.1 |
| 1985 | 13.5°C | 7.8°C | 2.2°C | 19.0°C | -2.9°C | 21 mm | 80% | 1.2 m/s | 2.6 |
| 1984 | 13.8°C | 8.7°C | 3.6°C | 18.7°C | 0.1°C | 9 mm | 87% | 1.4 m/s | 2.5 |
| 1983 | 14.1°C | 9.1°C | 4.1°C | 21.4°C | -1.4°C | 196 mm | 84% | 2 m/s | — |
| 1982 ❄️ | 10.8°C | 5.8°C | 0.9°C | 15.3°C | -4.9°C | 190 mm | 87% | 1.9 m/s | — |
| 1981 | 16.0°C | 10.7°C | 5.5°C | 21.7°C | 0.2°C | 144 mm | 75% | 1.9 m/s | — |
Actual recorded January data for each year, 1981–2025 — sourced from NASA POWER.
The average high in January is around 14°C with lows near 4.2°C (mean 9.1°C), based on 45 years of NASA POWER data.
January averages 105 mm of rainfall in Sunnyvale, a relatively wet time of year. The wettest on record was 309 mm in 2017.
The hottest January reached 23.4°C in 1994. The coldest dipped to -5.2°C in 1993.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average January temperatures have risen by about 1.2°C. Daytime highs moved from 13.6°C to 14.4°C and overnight lows from 3.3°C to 4.8°C over the same span.
January is one of the cooler months of the year in Sunnyvale and a relatively wet time of year, so plan for around 14°C daytime highs and 4.2°C at night.
Not quite — January is the 2nd coolest month in Sunnyvale, averaging 9.1°C.
For January in Sunnyvale, pack warm layers and a jacket for chilly mornings, with typical highs of 14°C and lows of 4.2°C. Bring an umbrella or light rain jacket too.
Relative humidity in January averages 83% — quite humid.
Average wind speed in January is 1.7 m/s. The windiest January on record averaged 2.8 m/s (1995).
The wettest January on record was 2017 with 309 mm. On average, January sees 105 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 Sunnyvale 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.
