Last updated: February 24, 2025
San Francisco in January offers a mild and varied climate, with average temperatures hovering around 11°C (52°F). The month sees a maximum of 21°C (70°F) on warmer days, while the chill sets in with lows reaching 3°C (38°F). January is also one of the wetter months, accumulating about 106 mm (4.2 in) of rain over approximately 9 days, contributing to a humidity level of around 85%. This blend of cool temperatures and intermittent rain makes for a unique, atmospheric experience, highlighting the city's signature coastal charm.
In January, San Francisco experiences a mild start to the year, with temperatures ranging from a minimum of 3°C (38°F) to a maximum of 21°C (70°F), resulting in an average of 11°C (52°F). This month marks the beginning of a gradual warming trend, as daytime highs comfortably touch the low 20s, ideal for exploring the city's iconic sights. As January transitions into February, temperatures remain stable but slightly rise, showcasing a min of 4°C (39°F) and a max of 20°C (69°F). Notably, the average remains unchanged at 11°C (52°F), hinting at a consistent climate with only minor variations. This pattern continues through March, maintaining similar averages while nudging nighttime lows higher. The city's temperatures hint at the charm of its transitional seasons, where impressive sunny days can occasionally surprise visitors, making it a delightful time for a winter getaway.
January marks a significant point in San Francisco's rainfall calendar, with an average precipitation of 106 mm (4.2 in) falling over 9 days. This places January as a key month for winter moisture, slightly lower than February's 109 mm (4.3 in), yet still substantially higher than the drier months that follow. As winter transitions into spring, precipitation levels drop sharply, with March receiving just 78 mm (3.1 in) over 10 days, and April's rainfall dwindling to 35 mm (1.4 in) across 5 days. This trend of decreasing precipitation continues into the summer months, where rainfall becomes a rarity, exemplifying San Francisco's characteristic dry season. Overall, January serves as a vital contributor to the city’s annual water supply, setting the stage for the months ahead as the rainfall gradually tapers off.
January marks one of the most humid months in San Francisco, with levels soaring to 85%. This high humidity sets the tone for the beginning of the year, as the city transitions to slightly lower moisture levels in February and March, both at 82%. The trend continues with a gradual decline through April, dropping to 79%, before experiencing a brief uptick in May at 83%. As summer approaches, humidity levels rise again, peaking in the warm months of July and August at 87%. Interestingly, the humidity begins to taper off in the fall, settling at 80% in October and further decreasing to 79% by year's end. Overall, San Francisco’s humidity exhibits a cyclical pattern, with notable peaks during mid-summer and lower averages in the spring and late fall.
In San Francisco, January greets residents with a moderate UV Index of 3, allowing for safe outdoor activities, with a burn time of about 30 minutes. As the year progresses, this index rises sharply, peaking in the summer months where June and July experience an extreme UV Index of 11 and a significantly reduced burn time of just 10 minutes. The trend indicates that while the early months offer more leisurely sun exposure, the late spring and summer demand increased vigilance against UV radiation. Notably, February follows with a still manageable UV Index of 5, and by March, the intensity escalates to a very high 8, signaling the start of the sun's more powerful influence. This year-round fluctuation emphasizes the importance of monitoring sun exposure throughout the seasons to protect skin health. For more detailed information on the UV Index trends throughout the year, visit San Francisco UV Index.
UV Risk Categories
In January, San Francisco welcomes the year with a modest 151 hours of sunshine, offering a cozy start to winter. As the weeks progress into February, the city begins to bask in an increase to 216 hours, signaling the approach of spring. With the arrival of March, the sunshine continues to build, reaching 263 hours, and by April, the days are getting noticeably longer with 296 hours of radiant light. The sun shines brightest in May and June, hitting peaks of 341 and 355 hours respectively, embodying the essence of the city's vibrant summer. However, as July transitions into late summer, there's a slight dip to 349 hours, followed by a gradual decline into autumn, with August at 320 hours, and subsequently September and October witnessing a steady fall, down to 299 and 276 hours respectively. The year wraps up with November and December bringing back a chill alongside 225 and 194 hours of sunshine, reflecting the cyclical nature of the seasons in this iconic city.
In January, San Francisco enjoys a 39% chance of sunny weather, marking it as one of the cooler months for sunshine in the city. This trend of limited sun continues into February, where the likelihood increases to 56%, suggesting that winter is slowly yielding to spring. As temperatures rise through March and April, the sun's embrace becomes even more pronounced, peaking in March with a 62% chance of sunny days. However, as summer approaches, the sunshine probability fluctuates again, dropping to 37% in July before gradually climbing back to the mid-40% range by August and September. Overall, while January isn't the sunniest month, it paves the way for increasing brightness as the year progresses.
In January, San Francisco experiences approximately 9 hours of daylight, setting the stage for a gradual increase as the months progress. As February arrives, daylight expands to 10 hours, followed by March, which sees a delightful 11 hours. The trend continues to climb, peaking in June, July, and most of May, where daylight stretches to a generous 14 hours. This abundance of light slowly recedes as summer transitions into fall, with August returning to 13 hours and September tapering to 12 hours. By November, daylight is back down to 10 hours, mirroring the 9 hours seen at the start of the year. This rhythmic ebb and flow of light throughout the year beautifully highlights the seasonal changes that characterize life in San Francisco.
In January, San Francisco greets the year with a gentle breeze, boasting an average wind speed of 3.2 m/s (7 mph). This marks the beginning of a gradual uptick in wind activity, as winter transitions into spring. By February, the winds pick up slightly to 4.0 m/s (9 mph), continuing to rise through the months, reaching 5.4 m/s (12 mph) by May. This steady increase reflects the city’s characteristic maritime climate, where the summer months typically bring a refreshing gust. As the summer peaks, the winds stabilize around 4.0 m/s in July and gradually drift back down through the fall and into winter, with November seeing a dip to 2.7 m/s (6 mph). This cyclical pattern illustrates San Francisco’s dynamic weather, where January’s calm start swiftly evolves into the vibrant winds of spring and summer before settling back into the quieter breezes of late fall.
The weather in San Francisco 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 San Francisco and find detailed weather information for every month.
January and February share similar temperature averages, with January witnessing slightly warmer highs of up to 21°C (70°F) compared to February’s peak of 20°C (69°F). Both months have minimal temperature variation, with January starting a bit cooler at a minimum of 3°C (38°F) compared to February's 4°C (39°F). Precipitation levels are also quite close, with January receiving 106 mm (4.2 in) and February slightly higher at 109 mm (4.3 in), both occurring over 9 days. Humidity remains relatively high in both months, though January is slightly more humid at 85% compared to February's 82%. For a detailed look at the February weather, you can visit San Francisco weather in February.
In comparing the weather between January and March, January typically experiences slightly cooler temperatures with a minimum of 3°C (38°F) and maximum of 21°C (70°F), while March sees a slight rise with a minimum of 5°C (42°F) and a maximum of 20°C (69°F). Precipitation levels are higher in January at 106 mm (4.2 in) over 9 days compared to March, which has 78 mm (3.1 in) but spreads across 10 days. Additionally, January has a higher humidity level at 85%, whereas March's humidity is slightly lower at 82%. For a more detailed look at March weather, check out San Francisco weather in March.
In January, the weather tends to be cooler, with temperatures ranging from a minimum of 3°C (38°F) to a maximum of 21°C (70°F) and an average of 11°C (52°F). This month also sees more precipitation, totaling 106 mm (4.2 in) over about 9 days, contributing to a high humidity level of 85%. In contrast, April ushers in warmer conditions with temperatures starting at a minimum of 7°C (44°F) and reaching up to 28°C (82°F), averaging 13°C (55°F). Precipitation decreases significantly to 35 mm (1.4 in) over 5 days, and humidity lowers to 79%. For a more detailed look at April's climate, you can visit San Francisco weather in April.
In January, the weather is relatively cool, with temperatures ranging from a minimum of 3°C (38°F) to a maximum of 21°C (70°F), and an average temperature of 11°C (52°F). This month experiences considerable rainfall, with a total precipitation of 106 mm (4.2 in) over approximately 9 days, coupled with high humidity at around 85%. In contrast, May brings warmer temperatures, with a minimum of 8°C (47°F) and a maximum reaching 24°C (75°F), offering a pleasant average of 14°C (57°F). May's weather is significantly drier, with only 20 mm (0.8 in) of precipitation over just 2 days, and humidity slightly lower at 83%. For more details, you can visit San Francisco weather in May.
In comparing the weather between January and June, January presents a cooler climate with average temperatures ranging from a minimum of 3°C (38°F) to a maximum of 21°C (70°F). This month also sees significant precipitation, totaling 106 mm (4.2 in) over 9 days, while humidity remains high at 85%. In contrast, June enjoys much milder temperatures, with an average ranging from 10°C (51°F) to a maximum of 31°C (88°F), and notably minimal precipitation of just 3 mm (0.1 in) over 0 days, with humidity slightly lower at 84%. For more detailed insights, you can check San Francisco weather in June.
The weather in January and July presents a striking contrast. In January, temperatures range from a minimum of 3°C (38°F) to a maximum of 21°C (70°F), with an average of 11°C (52°F). This month also experiences significant rainfall, totaling 106 mm (4.2 in) over approximately 9 days, contributing to a high humidity level of 85%. In stark comparison, July enjoys milder temperatures, with a minimum of 11°C (52°F) and a maximum of 24°C (76°F), averaging 15°C (60°F). Rainfall is minimal in July, with only 3 mm (0.1 in) recorded over no rainy days, and the humidity remains slightly elevated at 87%. For more details on July weather in San Francisco, you can visit San Francisco weather in July.
In January, the weather features a cooler temperature range with a minimum of 3°C (38°F) and a maximum of 21°C (70°F), leading to an average of 11°C (52°F). This month also experiences significant precipitation, with 106 mm (4.2 in) over 9 days, and humidity levels are relatively high at 85%. In contrast, August offers much milder conditions, showcasing a minimum temperature of 11°C (53°F) and a maximum of 27°C (81°F), resulting in an average of 16°C (61°F). The summer month sees minimal precipitation, with only 2 mm (0.1 in) and no rainy days, while humidity slightly increases to 87%. For more details about summer weather, check out San Francisco weather in August.
January and September showcase a striking contrast in weather patterns. In January, temperatures range from a cool 3°C (38°F) to a mild 21°C (70°F), accompanied by significant rainfall of 106 mm (4.2 in) spread over 9 days, leading to an average humidity of 85%. In contrast, September experiences warmer conditions with temperatures ranging from a minimum of 11°C (51°F) to a maximum of 35°C (96°F), while virtually no rain falls, resulting in only 2 mm (0.1 in) of precipitation over the entire month and humidity slightly higher at 86%. For a more detailed look at the typical weather in September, check out San Francisco weather in September.
When comparing the weather in January and October, notable differences emerge. January experiences cooler temperatures, with a minimum of 3°C (38°F) and an average of 11°C (52°F), while October is milder, featuring a minimum of 9°C (48°F) and an average of 16°C (60°F). Precipitation is also significantly higher in January, with 106 mm (4.2 in) falling over 9 days, compared to just 30 mm (1.2 in) across 2 days in October. Additionally, humidity levels remain relatively high in both months, but January holds a slight edge at 85% compared to October's 80%. For a more detailed look at the weather in October, you can refer to San Francisco weather in October.
In comparing the weather between January and November, we see that November tends to be slightly warmer with average temperatures ranging from 6°C (43°F) to 23°C (74°F), compared to January's range of 3°C (38°F) to 21°C (70°F). November also experiences less precipitation, with only 50 mm (2.0 in) over about 5 days, whereas January has 106 mm (4.2 in) spread across 9 days. Additionally, November's humidity levels are slightly lower at 79%, compared to January's more humid 85%. For a more detailed look at the pleasant weather typical of November, you can check out San Francisco weather in November.
In comparing the weather between January and December, both months feature a similar average temperature of 11°C (52°F), creating a mild climate overall. However, January tends to be slightly cooler, with a minimum temperature of 3°C (38°F) compared to December's 4°C (40°F). Precipitation levels are also higher in January, with 106 mm (4.2 in) recorded over nine days, versus December's 95 mm (3.7 in) over the same number of days. Additionally, January's humidity is notably higher at 85%, compared to December's 79%, making January feel a bit more humid and damp. For more details about December weather in San Francisco, you can visit San Francisco weather in December.
January in San Francisco brings a distinct chill compared to the milder months that bookend it. With temperatures dipping lower and a notable increase in precipitation, this month marks the heart of the winter season, featuring a blend of damp days and overcast skies. While the city enjoys a moderate climate overall, January's higher humidity makes it feel even cooler, often catching visitors off guard who expect San Francisco's usual sunshine. As you prepare for your trip, be sure to check out the full details on the city's weather patterns at San Francisco Climate to better equip yourself for the changing conditions.