January is one of the warmer months of the year in Halfmoon Bay, with average highs near 15°C and lows around 11.3°C (mean 13.2°C). It is a relatively wet time of year, averaging 121 mm of rainfall and 81% relative humidity across the period.
January is one of the warmer months of the year in Halfmoon Bay. Across 45 years of records, the warmest January in Halfmoon Bay was 2018 — when the month averaged 15.9°C — while the coldest were 1983 and 2017 at 11.8°C. Typical January days reach 15°C with nights near 11.3°C. The long-term January temperature trend is broadly flat.
January is a relatively wet time of year in Halfmoon Bay, averaging 121 mm of rainfall. The wettest January on record was 1982 with 241 mm, while the driest was 2018 at 43 mm.
Relative humidity in Halfmoon Bay during January averages 81%. The most humid January was 2005 at 86%, and the least humid was 2019 at 78%.
January receives about 5.8 kWh/m²/day of solar energy in Halfmoon Bay. The sunniest January was 2008 at 6.8 kWh/m²/day, and the cloudiest was 2017 at 5.1.
Average wind speed in Halfmoon Bay during January is 3.9 m/s. The windiest January was 2017 at 5.5 m/s, while the calmest were 1989 and 2018 at 2.6 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 13.4°C | 13.1°C | 12.9°C | 13.0°C | 13.6°C | +0.2°C |
| Avg High | 15.2°C | 15.0°C | 14.7°C | 14.9°C | 15.4°C | +0.2°C |
| Avg Low | 11.6°C | 11.2°C | 11.1°C | 11.1°C | 11.7°C | +0.1°C |
| Avg Rain | 158 mm | 117 mm | 122 mm | 111 mm | 83 mm | -75 mm |
January temperatures in Halfmoon Bay have risen by about 1°C between 1981–1985 and 2021–2025.
January has ranged from a record low of 7.3°C (1988) to a record high of 22.9°C (2018).
Rainfall in January is a relatively wet time of year, averaging 121 mm, with a wettest year of 241 mm.
One of the best times to visit Halfmoon Bay
January is one of the best times to visit Halfmoon Bay. Expect days averaging 15°C and nights around 11.3°C (mean 13.2°C) — warmer than Halfmoon Bay's yearly average — with higher rainfall (121 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 | 15.0°C | 13.2°C | 11.4°C | 17.7°C | 10.3°C | 57 mm | 80% | 3.1 m/s | 6.6 |
| 2024 | 15.5°C | 13.5°C | 11.6°C | 20.0°C | 8.3°C | 130 mm | 82% | 3.9 m/s | 6 |
| 2023 | 16.9°C | 14.8°C | 12.8°C | 21.2°C | 10.7°C | 47 mm | 79% | 2.7 m/s | 6.7 |
| 2022 | 15.6°C | 13.8°C | 12.0°C | 20.0°C | 9.1°C | 60 mm | 82% | 3.2 m/s | 5.8 |
| 2021 | 14.8°C | 13.2°C | 11.6°C | 20.2°C | 9.3°C | 133 mm | 83% | 4.2 m/s | 5.4 |
| 2020 | 14.7°C | 12.8°C | 10.9°C | 20.4°C | 9.1°C | 70 mm | 80% | 3.9 m/s | 6 |
| 2019 | 16.0°C | 14.2°C | 12.3°C | 21.0°C | 10.4°C | 99 mm | 78% | 4.6 m/s | 5.5 |
| 2018 🔥 | 18.2°C | 15.9°C | 13.6°C | 22.9°C | 9.8°C | 43 mm | 80% | 2.6 m/s | 6.5 |
| 2017 | 13.5°C | 11.8°C | 10.2°C | 17.1°C | 7.5°C | 139 mm | 80% | 5.5 m/s | 5.1 |
| 2016 | 14.0°C | 12.0°C | 10.1°C | 17.5°C | 7.9°C | 114 mm | 80% | 3.7 m/s | 5.6 |
| 2015 | 15.6°C | 13.7°C | 11.7°C | 19.2°C | 8.5°C | 60 mm | 80% | 3.9 m/s | 6.1 |
| 2014 | 13.7°C | 12.0°C | 10.4°C | 17.2°C | 8.4°C | 131 mm | 80% | 4.7 m/s | 5.5 |
| 2013 | 15.1°C | 13.2°C | 11.2°C | 19.7°C | 8.0°C | 161 mm | 81% | 4 m/s | 6.2 |
| 2012 | 14.3°C | 12.5°C | 10.6°C | 18.2°C | 7.9°C | 126 mm | 79% | 5.2 m/s | 5.7 |
| 2011 | 14.8°C | 13.0°C | 11.1°C | 18.5°C | 8.7°C | 110 mm | 80% | 4.1 m/s | 5.7 |
| 2010 | 13.9°C | 12.1°C | 10.3°C | 18.0°C | 7.9°C | 123 mm | 84% | 4 m/s | 5.6 |
| 2009 | 15.3°C | 13.4°C | 11.6°C | 20.6°C | 8.7°C | 185 mm | 83% | 3.6 m/s | 5.2 |
| 2008 | 16.0°C | 13.7°C | 11.4°C | 19.7°C | 9.9°C | 94 mm | 80% | 3.6 m/s | 6.8 |
| 2007 | 14.4°C | 12.5°C | 10.6°C | 19.0°C | 7.6°C | 103 mm | 82% | 3.7 m/s | 5.6 |
| 2006 | 14.7°C | 12.9°C | 11.2°C | 19.6°C | 8.7°C | 186 mm | 80% | 5.1 m/s | 6.2 |
| 2005 | 14.1°C | 12.5°C | 10.8°C | 18.2°C | 8.2°C | 147 mm | 86% | 3.4 m/s | 5.6 |
| 2004 | 15.1°C | 13.4°C | 11.7°C | 19.7°C | 8.6°C | 137 mm | 81% | 4 m/s | 6 |
| 2003 | 14.3°C | 12.5°C | 10.7°C | 18.1°C | 8.5°C | 131 mm | 83% | 4.1 m/s | 5.3 |
| 2002 | 15.5°C | 13.7°C | 11.9°C | 19.7°C | 8.5°C | 69 mm | 81% | 3.7 m/s | 5.8 |
| 2001 | 13.7°C | 12.0°C | 10.2°C | 18.7°C | 7.9°C | 85 mm | 79% | 4.2 m/s | 5.7 |
| 2000 | 14.3°C | 12.5°C | 10.6°C | 20.0°C | 7.9°C | 85 mm | 79% | 3 m/s | 5.5 |
| 1999 | 16.1°C | 13.7°C | 11.4°C | 19.9°C | 9.3°C | 85 mm | 79% | 3.2 m/s | 6.3 |
| 1998 | 14.7°C | 13.0°C | 11.3°C | 19.5°C | 7.3°C | 87 mm | 82% | 4.5 m/s | 5.9 |
| 1997 | 14.3°C | 12.5°C | 10.8°C | 17.9°C | 8.1°C | 62 mm | 82% | 3.7 m/s | 5.8 |
| 1996 | 15.2°C | 13.4°C | 11.5°C | 19.6°C | 9.4°C | 81 mm | 85% | 3.1 m/s | 5.7 |
| 1995 | 14.8°C | 12.7°C | 10.7°C | 21.0°C | 7.8°C | 99 mm | 80% | 3.8 m/s | 6.2 |
| 1994 | 15.1°C | 13.3°C | 11.4°C | 19.0°C | 7.7°C | 172 mm | 79% | 4 m/s | 5.7 |
| 1993 | 14.2°C | 12.4°C | 10.6°C | 18.8°C | 8.5°C | 196 mm | 80% | 5 m/s | 5.4 |
| 1992 | 15.5°C | 13.5°C | 11.5°C | 19.4°C | 8.0°C | 101 mm | 78% | 3.4 m/s | 6.2 |
| 1991 | 14.7°C | 12.9°C | 11.1°C | 19.5°C | 9.3°C | 194 mm | 82% | 3.7 m/s | 5.5 |
| 1990 | 15.2°C | 13.5°C | 11.8°C | 18.7°C | 9.6°C | 96 mm | 79% | 4.5 m/s | 5.9 |
| 1989 | 16.2°C | 14.3°C | 12.4°C | 19.3°C | 10.0°C | 75 mm | 84% | 2.6 m/s | 6 |
| 1988 | 14.9°C | 13.0°C | 11.1°C | 19.8°C | 7.3°C | 127 mm | 82% | 3.8 m/s | 5.8 |
| 1987 | 16.3°C | 14.5°C | 12.7°C | 20.9°C | 10.3°C | 143 mm | 82% | 3.6 m/s | 5.7 |
| 1986 | 16.6°C | 14.8°C | 13.0°C | 20.7°C | 9.1°C | 115 mm | 81% | 3.2 m/s | 5.8 |
| 1985 | 15.8°C | 13.9°C | 12.1°C | 19.7°C | 9.5°C | 186 mm | 83% | 3.4 m/s | 5.9 |
| 1984 | 14.0°C | 12.3°C | 10.5°C | 18.2°C | 8.5°C | 233 mm | 81% | 3.6 m/s | 5.7 |
| 1983 ❄️ | 13.4°C | 11.8°C | 10.2°C | 18.2°C | 7.4°C | 220 mm | 83% | 4.3 m/s | — |
| 1982 🌧️ | 14.4°C | 12.7°C | 11.0°C | 17.7°C | 8.3°C | 241 mm | 80% | 4.5 m/s | — |
| 1981 | 14.8°C | 12.9°C | 11.0°C | 19.9°C | 8.3°C | 85 mm | 79% | 4.5 m/s | — |
Actual recorded January data for each year, 1981–2025 — sourced from NASA POWER.
The average high in January is around 15°C with lows near 11.3°C (mean 13.2°C), based on 45 years of NASA POWER data.
January averages 121 mm of rainfall in Halfmoon Bay, a relatively wet time of year. The wettest on record was 241 mm in 1982.
The hottest January reached 22.9°C in 2018. The coldest dipped to 7.3°C in 1988.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average January temperatures have risen by about 1°C. Daytime highs moved from 14.5°C to 15.6°C and overnight lows from 11°C to 11.9°C over the same span.
January is one of the warmer months of the year in Halfmoon Bay and a relatively wet time of year, so plan for around 15°C daytime highs and 11.3°C at night.
Not quite — January is the 11th coolest month in Halfmoon Bay, averaging 13.2°C.
For January in Halfmoon Bay, pack light layers you can adjust through the day, with typical highs of 15°C and lows of 11.3°C. Bring an umbrella or light rain jacket too.
Relative humidity in January averages 81% — quite humid.
Average wind speed in January is 3.9 m/s. The windiest January on record averaged 5.5 m/s (2017).
The wettest January on record was 1982 with 241 mm. On average, January sees 121 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 Halfmoon Bay 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.
