January Weather in Half Moon Bay, United States

Last updated: February 24, 2025

In January, Half Moon Bay experiences a cool coastal climate characterized by a maximum temperature of 20°C (68°F) and an average of 11°C (53°F), dropping to a minimum of 5°C (41°F). This month is also notable for its high humidity, averaging around 85%, which contributes to a fresh maritime atmosphere. With precipitation totaling 102 mm (4.0 in) over approximately 9 days, January often brings a mix of rainy and dry spells, making it an ideal time for those who appreciate the beauty of winter along the picturesque California coast.

January Temperature in Half Moon Bay

In January, Half Moon Bay experiences a mild winter, with temperatures ranging from a cool 5°C (41°F) to a pleasant 20°C (68°F). The average temperature hovers around 11°C (53°F), providing a comfortable respite for those looking to escape harsher climates. As the month progresses, patterns emerge; the low temperatures remain consistently steady, while the maximum temperatures offer a glimpse of spring's early warmth. January marks a transitional period within a year characterized by gradual increases in temperature, especially as it shifts into February, where the range stays nearly identical. This stability hints at the region’s temperate maritime climate, making it an appealing destination for outdoor enthusiasts, despite the winter chill.

January Weather in Half Moon Bay: Daily Temperature Highs, Lows, and Averages

The chart illustrates January temperature patterns in Half Moon Bay, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec525253545558586062595653
Data source: Temperature data for Half Moon Bay generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

January Precipitation in Half Moon Bay

In January, Half Moon Bay experiences a notable precipitation peak, receiving 102 mm (4.0 inches) of rain over approximately 9 days. This robust rainfall sets the tone for the winter months, as February closely follows with a similar amount of 101 mm (4.0 inches). As the seasons transition into spring, precipitation begins to taper off significantly; by April, it drops to just 34 mm (1.3 inches) over only 5 days, indicating a shift towards a drier climate. The pattern is clear: as winter wanes, the rainfall lessens dramatically, with June and July seeing virtually no precipitation at all. Interestingly, this trend of decreasing rain continues into the summer months, with the return of wetter conditions only arriving in late fall, when November brings 48 mm (1.9 inches) of rain, followed by 92 mm (3.6 inches) in December. Overall, January's rainfall serves as a vital reminder of the region's characteristic winter wetness, highlighted by a stark contrast to the arid summer months that follow.

January Precipitation Trends in Half Moon Bay

The chart displays monthly precipitation patterns in Half Moon Bay, with values for each month alongside January's data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how January's conditions compare to those of other months.
JanFebMarAprMayJunJulAugSepOctNovDec1021017834224333274892
Data source: Precipitation data for January generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

January Humidity in Half Moon Bay

In January, Half Moon Bay experiences a notably high humidity level of 85%, setting the stage for the damp, misty climate typical of coastal California winters. As the month transitions into February and March, humidity remains relatively consistent at 82%, providing a subtle cushion of moisture. By April, a slight decrease to 79% signals the onset of spring, though humidity begins to creep back up with May and June rolling in at 83% and 84% respectively. The summer months bring an increase, peaking at 87% in both July and August, creating a muggy atmosphere that contrasts the earlier dryness. As September settles in, humidity slightly drops to 86%, gradually cooling down to 80% by October, before returning to autumnal lows of 79% in November and December. This cyclical pattern illustrates a coastal climate that leans on high humidity during the winter and summer months while experiencing a brief reprieve in the spring and fall.

January Average Humidity in Half Moon Bay

This chart illustrates the average monthly humidity levels in Half Moon Bay, with January's data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, allowing you to see how January's humidity levels compare to other months.
JanFebMarAprMayJunJulAugSepOctNovDec85%82%82%79%83%84%87%87%86%80%79%79%
Data source: Humidity data for January generated using information from the Copernicus Climate Change Service.

January UV Index in Half Moon Bay

In January, Half Moon Bay experiences a moderate UV Index of 3, allowing for around 30 minutes of sun exposure before risk of burning increases. As the month progresses into February, the UV Index rises to 5, still categorized as moderate, maintaining the same burn time. By March, the sun’s intensity escalates dramatically to an 8 on the UV scale, classified as very high, cutting burn time down to just 15 minutes. This trend continues into April and May, where the UV Index peaks at 9 and 10 respectively, highlighting a critical need for sun protection during these months. The summer months, June and July, see the UV Index reach its highest at 11, marked as extreme, which significantly reduces safe exposure to only 10 minutes. However, as autumn arrives, the UV levels start to taper off, with October seeing a 7 and a burn time of 25 minutes, before returning to a more moderate 4 in November and dropping back to 3 in December. This cyclical pattern exhibits how the UV Index varies seasonally, underscoring the importance of monitoring these levels for safe outdoor activities throughout the year. For more detailed information, visit the Half Moon Bay UV Index.

Maximum UV Index Levels in Half Moon Bay for January

The chart shows the monthly maximum UV Index (UVI) for Half Moon Bay in January, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues.
JanFebMarAprMayJunJulAugSepOctNovDec3589101111109743
Data source: Half Moon Bay January UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

January Sunshine in Half Moon Bay

In January, Half Moon Bay experiences a modest 151 hours of sunshine, marking the start of the year with a gentle embrace of light. As the months progress, sunshine hours steadily increase, reaching 216 hours in February and further climbing to 263 hours in March, heralding the transition into spring. By April, sunshine peaks at 296 hours, and this upward trend continues, peaking in June with an impressive 355 hours. The summer months bask in ample sunlight, creating perfect beach days, but as August transitions into fall, the hours begin to recede. By October, the sun only shines 276 hours, and the decline continues into the winter months, closing out the year with 194 hours in December. This rhythmic ebb and flow of sunshine underscores the coastal charm of Half Moon Bay, where each season brings its own unique blend of light and warmth.

Monthly Sunshine Duration in Half Moon Bay: January Highlighted

The January sunshine duration represents the total number of hours Half Moon Bay experiences direct sunlight during the month of January, excluding cloudy or obstructed periods. This chart compares the sunshine duration of January with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec151h216h263h296h341h355h349h320h299h276h225h194h
Data source: Half Moon Bay January Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Half Moon Bay During January

In Half Moon Bay, January brings a modest 39% chance of sunny weather, making it one of the cloudier months of the year. As we progress into February, the likelihood of sunshine rises significantly to 56%, signaling the start of a brighter period. The sunshine potential continues to climb, peaking at 60% in March before experiencing a slight dip to 44% in April. As spring approaches, the chances of sunny days remain relatively stable, hovering around the mid to upper 40s through June. Interestingly, the warmth of summer sees a decrease in sunshine likelihood, with July dropping to just 30%. However, daylight begins to improve again as the year nears its end, with October and November both offering about 50% and 43% chances respectively. Overall, while January may not be the sunniest month, the trend points towards brighter days as winter transitions into spring.

Percentage of Sunny Days in January in Half Moon Bay

The chart illustrates the percentage of sunny days in Half Moon Bay throughout the year, with January highlighted. It highlights the variation in sunshine across each month and provides an overview of the typical frequency of sunny days, offering insights into how often Half Moon Bay experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec39%56%60%44%57%45%30%43%47%50%43%35%
Data source: Half Moon Bay January chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Half Moon Bay in January

In Half Moon Bay, United States, January greets residents with 9 hours of daylight, a time when the days are still short and winter's chill lingers. As the month progresses into February, daylight subtly increases to 10 hours, hinting at the approaching spring. March sees a more noticeable change, expanding to 11 hours of daylight, while April blooms further with 13 hours. This trend continues into May and June, when the days stretch to a vibrant 14 hours, allowing for ample hours of sunshine and outdoor activities. Come July, the daylight duration remains stable at 14 hours, before gradually tapering off in August to 13 hours. The shift continues into the fall months; September offers 12 hours, with daylight dwindling to 11 hours in October. November and December close the year with 10 and 9 hours of daylight respectively, returning to the shorter days of winter. This cyclical pattern highlights the seasonal rhythm of light that defines life in this coastal town.

Average Daylight Hours in Half Moon Bay for January

The chart illustrates the variation in daylight duration in Half Moon Bay throughout the year, with January highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec9h 54m10h 49m11h 59m13h 11m14h 11m14h 41m14h 25m13h 31m12h 22m11h 10m10h 8m9h 36m
Data source: Half Moon Bay daylight hours, calculated by summing the hours between sunrise and sunset for each day.

January Winds in Half Moon Bay

In January, the winds in Half Moon Bay are relatively gentle, with an average speed of 3.5 m/s (8 mph), setting a calm tone for the new year. As winter transitions to spring, wind speeds gradually increase, peaking in May at 5.4 m/s (12 mph), hinting at the lively breezes to come. Interestingly, June sees a slight dip back to 4.3 m/s (10 mph), maintaining a consistent feel into the summer months. The wind begins to lose its vigor as the year progresses, dropping to its annual low of 3.1 m/s (7 mph) in September and November, creating a tranquil atmosphere as autumn settles in. Overall, January's mild breezes are just the beginning of a dynamic wind pattern that ebbs and flows with the seasons.

Average January Wind Speed in Half Moon Bay

The chart displays monthly wind speed patterns in Half Moon Bay, with values for each month shown alongside January's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how January's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec3.5 m/s4.34.24.55.44.33.43.33.13.83.04.1
Data source: Half Moon Bay January wind data, generated using information from the Copernicus Climate Change Service.

How January Weather in Half Moon Bay Compares to Other Months

The weather in Half Moon Bay changes throughout the year, offering a unique experience in each season. Below is a month-by-month comparison of January's weather with other months, highlighting differences in temperature, precipitation, and other key factors. Click on each section to discover seasonal trends in Half Moon Bay and find detailed weather information for every month.

January and February share similar weather patterns, with both months experiencing a minimum temperature of 5°C (41°F) and an average temperature of 11°C (53°F). The maximum temperature in February reaches 20°C (69°F), just slightly higher than January's max of 20°C (68°F). Precipitation levels are comparable, with January receiving 102 mm (4.0 in) and February recording 101 mm (4.0 in), both spread over 9 days. Humidity is slightly higher in January at 85%, while February sees a decrease to 82%. For a more detailed look at February's climate, visit Half Moon Bay weather in February.

In January, the weather features slightly milder temperatures, with a minimum of 5°C (41°F) and a maximum reaching 20°C (68°F), while the average hovers around 11°C (53°F). The month experiences substantial precipitation at 102 mm (4.0 in) over approximately 9 days, and humidity levels are relatively high at 85%. In contrast, March brings slightly warmer temperatures, with minimums of 7°C (44°F) and maximums of 19°C (67°F), resulting in an average of 12°C (53°F). Precipitation decreases to 77 mm (3.0 in) and is spread across 11 days, leading to a slightly lower humidity of 82%. For a more detailed look at what to expect, you can visit Half Moon Bay weather in March.

In comparing the weather between January and April, we see a noticeable increase in temperatures. January features a minimum of 5°C (41°F) and averages around 11°C (53°F), while April sees slightly warmer temperatures with a minimum of 7°C (45°F) and an average of 12°C (55°F). Additionally, the maximum temperature rises more significantly from 20°C (68°F) in January to 25°C (78°F) in April. Precipitation also decreases in April, with only 34 mm (1.3 in) over 5 days compared to January's 102 mm (4.0 in) across 9 days, which contributes to lower humidity levels in April at 79% compared to January's 85%. For more detailed insights, you can check Half Moon Bay weather in April.

In January, the weather tends to be cooler with temperatures ranging from a minimum of 5°C (41°F) to a maximum of 20°C (68°F), and an average temperature of 11°C (53°F). This month experiences significant precipitation, totaling 102 mm (4.0 in) over about 9 days, alongside a humidity level of 85%. In contrast, May sees slightly warmer temperatures, with a minimum of 9°C (48°F), an average of 13°C (56°F), and a maximum of 21°C (69°F). Notably, May enjoys much less rainfall, with only 22 mm (0.9 in) of precipitation across just 2 days, coupled with a similar humidity level of 83%. For more detailed information, you can check out Half Moon Bay weather in May.

In January, the weather is generally cooler with temperatures ranging from a minimum of 5°C (41°F) to a maximum of 20°C (68°F) and an average of 11°C (53°F). This month also sees significant precipitation, totaling 102 mm (4.0 in) over about 9 days, making it one of the wetter months, while humidity hovers around 85%. In contrast, June offers milder conditions with minimum temperatures of 10°C (51°F) and maximums reaching 27°C (81°F), providing an average temperature of 15°C (58°F). Remarkably, June experiences minimal precipitation of only 4 mm (0.2 in) without any rainy days, with humidity slightly lower at 84%. For more detailed information about the weather during this month, you can check Half Moon Bay weather in June.

The weather in January is notably cooler than in July, with average temperatures ranging from a minimum of 5°C (41°F) to a maximum of 20°C (68°F). In contrast, July tends to be milder, with temperatures starting at a minimum of 11°C (51°F) and peaking at the same maximum of 20°C (69°F). January sees a substantial amount of rainfall, with 102 mm (4.0 in) spread over 9 days, while July is much drier, recording only 3 mm (0.1 in) with no rainy days. The humidity levels are quite consistent between the two months, hovering around 85% in January and 87% in July. For a more detailed look at July's weather, you can visit Half Moon Bay weather in July.

In January, the weather in Half Moon Bay experiences cooler temperatures, with a minimum of 5°C (41°F) and an average of 11°C (53°F), peaking at a maximum of 20°C (68°F). This month also sees significant rainfall, averaging 102 mm (4.0 in) over about 9 days, contributing to a relatively high humidity of 85%. In contrast, August offers a noticeable warming with minimum temperatures of 11°C (53°F) and an average of 16°C (61°F), reaching up to 24°C (76°F). Remarkably, it is a dry month with only 3 mm (0.1 in) of precipitation and no rainy days, while humidity remains slightly higher at 87%. For more details, check out Half Moon Bay weather in August.

In comparing the weather of January and September, January tends to be cooler with a minimum temperature of 5°C (41°F) and an average of 11°C (53°F), while September enjoys milder conditions, ranging from a minimum of 11°C (52°F) to an average of 16°C (62°F). The maximum temperatures also reflect this seasonal shift, with January peaking at 20°C (68°F) compared to September’s warmer high of 31°C (88°F). Rainfall is notably more prevalent in January, receiving 102 mm (4.0 in) over 9 days, while September boasts dry conditions with only 3 mm (0.1 in) and no precipitation days. Humidity levels are similarly high in both months, standing at 85% in January and 86% in September. For more detailed information, you can check Half Moon Bay weather in September.

In comparing January and October weather, we see notable differences in temperature and precipitation. January experiences cooler temperatures, with averages ranging from a minimum of 5°C (41°F) to a maximum of 20°C (68°F), while October is milder, with minimums around 9°C (49°F) and maximums reaching 27°C (80°F). Additionally, January is much wetter, receiving 102 mm (4.0 in) of precipitation over 9 days, compared to October's relatively dry climate, which sees just 27 mm (1.1 in) across only 2 days. Humidity levels are slightly higher in January at 85%, while October maintains a comfortable 80%. For a detailed look at October weather patterns, you can check out Half Moon Bay weather in October.

January and November exhibit some notable differences in weather patterns. January tends to be slightly cooler, with average temperatures ranging from a minimum of 5°C (41°F) to a maximum of 20°C (68°F). In contrast, November sees a milder range with minimums of 7°C (45°F) and maximums of 21°C (70°F). Precipitation also plays a significant role; January experiences more rainfall at 102 mm (4.0 in) over 9 days, while November is much drier with only 48 mm (1.9 in) spread across 5 days. Humidity levels are higher in January at 85%, compared to November's 79%. For more details on November weather, check out Half Moon Bay weather in November.

In comparing the weather of January and December, both months exhibit mild temperatures, but January tends to be slightly cooler overall. The minimum temperature in January averages at 5°C (41°F), while December has a slightly higher minimum of 6°C (44°F). Both months share a similar average temperature of around 11°C (53°F), while the maximum temperatures remain quite close, with January reaching 20°C (68°F) and December peaking at 19°C (67°F).

January sees a bit more precipitation, totaling 102 mm (4.0 in) over 9 days, compared to December's 92 mm (3.6 in) across 10 days, indicating that January is slightly wetter. Additionally, the humidity is higher in January at 85%, compared to December's 79%. For a more detailed insight into December's weather specifics, you can check out Half Moon Bay weather in December.

Compare Half Moon Bay's Climate with Cities Worldwide

Conclusion: What to Expect From January Weather in Half Moon Bay

January in Half Moon Bay brings a distinct chill and a hint of nostalgia, contrasting the warmer months. With temperatures averaging around 11°C (53°F), the month feels invigorating yet crisp, perfect for those who enjoy brisk coastal air. While precipitation is notably higher than in the summer, with 102 mm (4.0 in) falling over about 9 days, the moisture nourishes the lush landscapes, making for picturesque scenery. The high humidity of 85% adds to the cool ambiance, creating a unique coastal mood. For those wishing to delve deeper into the climatic details of this beautiful coastal town, explore Half Moon Bay Climate.