January is one of the cooler months of the year in San Mateo, with average highs near 13.3°C and lows around 8.6°C (mean 11°C). It is a relatively wet time of year, averaging 99 mm of rainfall and 83% relative humidity across the period.
January is one of the cooler months of the year in San Mateo. Across 45 years of records, the warmest Januarys in San Mateo were 1986, 1998 and 2003 — when the month averaged 12.6°C — while the coldest was 1982 at 8.7°C. Typical January days reach 13.3°C with nights near 8.6°C. The long-term trend is warming, about 0.2°C per decade.
January is a relatively wet time of year in San Mateo, averaging 99 mm of rainfall. The wettest January on record was 2017 with 276 mm, while the driest was 2015 at 2 mm.
Relative humidity in San Mateo during January averages 83%. The most humid January was 2003 at 91%, and the least humid was 2014 at 72%.
January receives about 2.4 kWh/m²/day of solar energy in San Mateo. 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 San Mateo during January is 3.6 m/s. The windiest January was 1995 at 5.3 m/s, while the calmest was 2015 at 2.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 10.6°C | 11.1°C | 10.5°C | 11.3°C | 11.4°C | +0.8°C |
| Avg High | 13.2°C | 13.4°C | 12.8°C | 13.7°C | 13.7°C | +0.5°C |
| Avg Low | 8.1°C | 8.7°C | 8.1°C | 8.8°C | 9.2°C | +1.1°C |
| Avg Rain | 92 mm | 122 mm | 86 mm | 101 mm | 90 mm | -2 mm |
January temperatures in San Mateo have risen by about 0.8°C between 1981–1985 and 2021–2025.
January has ranged from a record low of 1.8°C (1997) to a record high of 19.5°C (2014).
Rainfall in January is a relatively wet time of year, averaging 99 mm, with a wettest year of 276 mm.
A quieter season to visit San Mateo
If your dates are flexible, the more temperate months of September and August tend to be the most comfortable for visiting San Mateo. That said, January — with days averaging 13.3°C and nights around 8.6°C (mean 11°C) and higher rainfall (99 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 | 13.7°C | 11.1°C | 8.5°C | 16.6°C | 6.3°C | 11 mm | 83% | 2.8 m/s | 2.8 |
| 2024 | 14.2°C | 12.3°C | 10.5°C | 19.2°C | 7.7°C | 149 mm | 88% | 3.8 m/s | 2.2 |
| 2023 | 12.9°C | 10.9°C | 8.9°C | 16.2°C | 4.7°C | 238 mm | 83% | 5 m/s | 2.4 |
| 2022 | 14.2°C | 11.5°C | 8.9°C | 16.5°C | 6.2°C | 6 mm | 85% | 2.7 m/s | 2.7 |
| 2021 | 13.7°C | 11.3°C | 9.0°C | 18.9°C | 5.8°C | 97 mm | 84% | 3.2 m/s | 2.5 |
| 2020 | 13.3°C | 11.3°C | 9.3°C | 16.9°C | 6.9°C | 42 mm | 88% | 3.3 m/s | 2.4 |
| 2019 | 14.4°C | 12.3°C | 10.2°C | 17.2°C | 5.5°C | 136 mm | 83% | 3.8 m/s | 2.2 |
| 2018 | 14.3°C | 12.2°C | 10.0°C | 17.0°C | 7.8°C | 124 mm | 87% | 3 m/s | 2.2 |
| 2017 🌧️ | 12.0°C | 10.0°C | 7.9°C | 15.3°C | 3.8°C | 276 mm | 84% | 4.4 m/s | 2.4 |
| 2016 | 13.7°C | 12.0°C | 10.3°C | 15.7°C | 4.2°C | 165 mm | 86% | 3.7 m/s | 2 |
| 2015 | 15.0°C | 12.4°C | 9.8°C | 18.2°C | 5.3°C | 2 mm | 84% | 2.4 m/s | 2.8 |
| 2014 | 15.9°C | 12.5°C | 9.2°C | 19.5°C | 6.8°C | 5 mm | 72% | 2.6 m/s | 2.8 |
| 2013 | 12.3°C | 9.5°C | 6.6°C | 15.8°C | 2.9°C | 17 mm | 80% | 3.6 m/s | 2.9 |
| 2012 | 13.4°C | 10.6°C | 7.8°C | 17.3°C | 4.9°C | 79 mm | 79% | 3.4 m/s | 2.6 |
| 2011 | 12.9°C | 10.2°C | 7.6°C | 17.3°C | 3.0°C | 34 mm | 86% | 3.2 m/s | 2.5 |
| 2010 | 12.9°C | 11.0°C | 9.0°C | 14.7°C | 6.1°C | 175 mm | 89% | 3.8 m/s | 2 |
| 2009 | 14.0°C | 10.7°C | 7.3°C | 18.7°C | 4.5°C | 40 mm | 77% | 3.4 m/s | 2.7 |
| 2008 | 11.6°C | 9.5°C | 7.4°C | 15.6°C | 4.5°C | 200 mm | 84% | 4.5 m/s | 2 |
| 2007 | 11.9°C | 9.1°C | 6.4°C | 14.9°C | 2.5°C | 14 mm | 79% | 3.6 m/s | 2.9 |
| 2006 | 13.1°C | 11.1°C | 9.0°C | 16.2°C | 6.0°C | 94 mm | 86% | 3.5 m/s | 2.5 |
| 2005 | 12.9°C | 10.7°C | 8.4°C | 15.4°C | 4.3°C | 107 mm | 85% | 3.7 m/s | 2.4 |
| 2004 | 12.4°C | 10.6°C | 8.7°C | 15.3°C | 4.9°C | 66 mm | 87% | 3.6 m/s | 2.2 |
| 2003 | 14.7°C | 12.6°C | 10.4°C | 17.0°C | 7.5°C | 36 mm | 91% | 2.7 m/s | 2.3 |
| 2002 | 11.7°C | 9.5°C | 7.3°C | 14.7°C | 3.6°C | 48 mm | 85% | 3.4 m/s | 2.6 |
| 2001 | 12.9°C | 10.2°C | 7.5°C | 17.7°C | 3.5°C | 103 mm | 79% | 3.9 m/s | 2.6 |
| 2000 | 12.6°C | 10.8°C | 8.9°C | 15.1°C | 5.1°C | 148 mm | 89% | 3.4 m/s | 2.1 |
| 1999 | 12.5°C | 10.0°C | 7.5°C | 15.8°C | 3.8°C | 104 mm | 85% | 3.7 m/s | 2.4 |
| 1998 | 14.0°C | 12.6°C | 11.2°C | 16.5°C | 8.5°C | 185 mm | 86% | 4 m/s | 2 |
| 1997 | 13.0°C | 11.0°C | 9.0°C | 15.3°C | 1.8°C | 166 mm | 87% | 3.8 m/s | 2.2 |
| 1996 | 13.5°C | 11.4°C | 9.3°C | 16.4°C | 7.3°C | 132 mm | 85% | 3.8 m/s | 2.2 |
| 1995 | 13.2°C | 11.8°C | 10.4°C | 17.6°C | 7.3°C | 229 mm | 88% | 5.3 m/s | 1.9 |
| 1994 | 14.3°C | 11.2°C | 8.2°C | 18.8°C | 5.0°C | 44 mm | 82% | 3.3 m/s | 2.7 |
| 1993 | 12.8°C | 10.3°C | 7.8°C | 16.2°C | 2.6°C | 203 mm | 81% | 4.5 m/s | 2.3 |
| 1992 | 13.8°C | 10.8°C | 7.8°C | 15.7°C | 5.5°C | 68 mm | 82% | 3.5 m/s | 2.7 |
| 1991 | 13.5°C | 10.6°C | 7.7°C | 17.2°C | 4.9°C | 12 mm | 79% | 2.7 m/s | 2.5 |
| 1990 | 13.5°C | 10.9°C | 8.4°C | 16.8°C | 5.3°C | 76 mm | 83% | 4.2 m/s | 2.7 |
| 1989 | 12.2°C | 9.2°C | 6.2°C | 16.1°C | 3.4°C | 27 mm | 82% | 3.5 m/s | 2.7 |
| 1988 | 13.0°C | 10.7°C | 8.4°C | 18.0°C | 5.2°C | 89 mm | 82% | 3.6 m/s | 2.2 |
| 1987 | 13.0°C | 10.3°C | 7.7°C | 16.5°C | 3.4°C | 67 mm | 77% | 3.9 m/s | 2.5 |
| 1986 🔥 | 14.7°C | 12.6°C | 10.5°C | 18.2°C | 7.0°C | 101 mm | 83% | 3.5 m/s | 2.1 |
| 1985 | 12.8°C | 9.9°C | 7.1°C | 17.4°C | 3.6°C | 44 mm | 80% | 2.7 m/s | 2.6 |
| 1984 | 13.1°C | 10.7°C | 8.2°C | 16.5°C | 5.9°C | 10 mm | 86% | 3.1 m/s | 2.5 |
| 1983 | 14.2°C | 11.6°C | 9.0°C | 18.2°C | 5.4°C | 182 mm | 80% | 4.3 m/s | — |
| 1982 ❄️ | 11.2°C | 8.7°C | 6.1°C | 13.4°C | 1.9°C | 186 mm | 82% | 4.3 m/s | — |
| 1981 | 14.6°C | 12.1°C | 9.6°C | 18.1°C | 5.9°C | 124 mm | 78% | 4.2 m/s | — |
Actual recorded January data for each year, 1981–2025 — sourced from NASA POWER.
The average high in January is around 13.3°C with lows near 8.6°C (mean 11°C), based on 45 years of NASA POWER data.
January averages 99 mm of rainfall in San Mateo, a relatively wet time of year. The wettest on record was 276 mm in 2017.
The hottest January reached 19.5°C in 2014. The coldest dipped to 1.8°C in 1997.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average January temperatures have risen by about 0.8°C. Daytime highs moved from 13.2°C to 13.7°C and overnight lows from 8°C to 9.2°C over the same span.
January is one of the cooler months of the year in San Mateo and a relatively wet time of year, so plan for around 13.3°C daytime highs and 8.6°C at night.
Yes — January is the coldest month of the year in San Mateo, averaging 11°C.
For January in San Mateo, pack light layers you can adjust through the day, with typical highs of 13.3°C and lows of 8.6°C. Bring an umbrella or light rain jacket too.
Relative humidity in January averages 83% — quite humid.
Average wind speed in January is 3.6 m/s. The windiest January on record averaged 5.3 m/s (1995).
The wettest January on record was 2017 with 276 mm. On average, January sees 99 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 San Mateo 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.
