December Weather in Mill Valley, United States

Last updated: February 24, 2025

In Mill Valley, United States, December brings a refreshing climate characterized by a maximum temperature of 22°C (72°F) and an average of 10°C (51°F), providing a mild winter atmosphere. The month experiences a minimum temperature of 3°C (38°F), ensuring chilly nights. With a notable precipitation amount of 98 mm (3.9 in) over 9 rainy days, the humidity levels hover around 79%, creating a crisp and invigorating environment. This combination of temperatures and moisture makes December a unique time to enjoy the natural beauty of Mill Valley.

December Temperature in Mill Valley

In Mill Valley, United States, December ushers in the cooler winter months with temperatures tapering off from the milder conditions of fall. The month showcases a minimum of 3°C (38°F), while the average temperature settles at around 10°C (51°F), allowing for cozy outdoor enjoyment. Daytime highs reach up to 22°C (72°F), still retaining a hint of warmth reminiscent of late autumn. This gradual cooling trend reflects a shift from the warmer averages seen in the preceding months, yet December maintains a pleasant climate that encourages residents and visitors alike to savor the gentle transition into winter's embrace.

December Weather in Mill Valley: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Mill Valley, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec515253575963636465625551
Data source: Temperature data for Mill Valley generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Mill Valley

In December, Mill Valley experiences a notable uptick in precipitation, with a total of 98 mm (3.9 in) falling over 9 days. This marks a significant increase from the drier months of summer, where rainfall was nearly nonexistent, contributing to a refreshing transition into winter. The consistent precipitation throughout the month sets the stage for the rainy season, as December's totals align closely with the generally wetter months that precede it, particularly January and February. Compared to November's 48 mm (1.9 in) over just 5 days, December not only showcases a resurgence in rainfall but also reinforces the trend of increasing moisture as the year draws to a close, highlighting Mill Valley's diverse climate dynamics.

December Precipitation Trends in Mill Valley

The chart displays monthly precipitation patterns in Mill Valley, with values for each month alongside December's data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December's conditions compare to those of other months.
JanFebMarAprMayJunJulAugSepOctNovDec1111168035202212304898
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

December Humidity in Mill Valley

In Mill Valley, United States, December marks a transition into the winter months, characterized by a drop in humidity to 79%. This figure aligns with the lower humidity levels observed in November, suggesting a trend towards drier conditions as the year comes to a close. Throughout the year, humidity peaks in the warmer months of July and August, where it reaches a high of 87%, before tapering off significantly. The gradual decline from early summer through to winter highlights a seasonal ebb in moisture, contributing to the region's varied climate. As a result, December offers a refreshing reprieve from the heavy summer humidity, setting the stage for a serene winter atmosphere.

December Average Humidity in Mill Valley

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

December UV Index in Mill Valley

In Mill Valley, December experiences a moderate UV Index of 3, which indicates a 30-minute burn time for fair-skinned individuals. This marks a return to lower UV levels after the peak summer months, when the index soared to extreme heights of 11 in June and July. As the year draws to a close, residents and visitors can enjoy the outdoors with relatively less concern about UV exposure, compared to the intense rays encountered in the spring and summer. It’s a reminder of the cyclical nature of UV exposure, highlighting the importance of adjusting sun protection measures through the seasons. For a comprehensive look at UV trends throughout the year, visit Mill Valley UV Index.

Maximum UV Index Levels in Mill Valley for December

The chart shows the monthly maximum UV Index (UVI) for Mill Valley in December, 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.
JanFebMarAprMayJunJulAugSepOctNovDec3589101111109643
Data source: Mill Valley December 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.

December Sunshine in Mill Valley

In Mill Valley, December marks a transition in sunlight as the year begins to close. With 191 hours of sunshine, the month provides a brief respite following the cooler, cloudier days of late autumn. While December may not bask in the abundant light of summer months like July, which enjoys an impressive 386 hours, it still contributes to a pleasant atmosphere for enjoying outdoor activities and the festive spirit. As the seasons shift, there's a noticeable decline from the peak 356 hours in May, highlighting a trend of decreasing daylight. Yet, this decrease in sunshine is embraced by the community, as residents find joy in the cozy ambiance of the season, balancing the dwindling light with warm gatherings and scenic winter landscapes.

Monthly Sunshine Duration in Mill Valley: December Highlighted

The December sunshine duration represents the total number of hours Mill Valley experiences direct sunlight during the month of December, excluding cloudy or obstructed periods. This chart compares the sunshine duration of December with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec148h215h263h299h356h378h386h348h312h280h224h191h
Data source: Mill Valley December Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Mill Valley During December

In Mill Valley, the likelihood of enjoying sunny weather in December dips to 30%, reflecting a seasonal trend towards cloudier days as winter approaches. Following a steady progression from a 39% chance in January, the sun's presence peaks in May at 75% before gradually declining through the summer months. While December’s sunlight is scarce, it’s part of a broader pattern where the chances increase significantly from February’s 56% to April’s 66%. As the year draws to a close, residents can expect shorter, less sunny days, signaling a shift away from the warmer, bright months.

Percentage of Sunny Days in December in Mill Valley

The chart illustrates the percentage of sunny days in Mill Valley throughout the year, with December 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 Mill Valley experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec39%56%63%66%75%65%51%60%62%52%42%30%
Data source: Mill Valley December chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Mill Valley in December

As December rolls into Mill Valley, the daylight hours dip back down to 9 hours, mirroring the brief light of January. This seasonal decline is part of a natural rhythm where the year begins with 9 hours of daylight, gradually increasing to a peak of 14 hours from May through July. Following the summer solstice, daylight begins to wane, cascading down through the colors of autumn, reaching 10 hours in November before settling in for the winter months. This trend illustrates a gradual shift from longer, sun-soaked days to the cozy, shorter daylight hours of winter, inviting an appreciation for the beauty and uniqueness of each season.

Average Daylight Hours in Mill Valley for December

The chart illustrates the variation in daylight duration in Mill Valley throughout the year, with December highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec9h 51m10h 47m11h 59m13h 12m14h 14m14h 44m14h 27m13h 32m12h 22m11h 9m10h 5m9h 33m
Data source: Mill Valley daylight hours, calculated by summing the hours between sunrise and sunset for each day.

December Winds in Mill Valley

In Mill Valley, December brings a gentle breeze with an average wind speed of 3.2 m/s (7 mph), a slight uptick from the calmer November days when winds hovered at 2.2 m/s (5 mph). The transition from fall to winter sees a modest recovery in wind strength, reminiscent of the steady increase observed from the early months of the year. Historically, January begins with the softest winds at 2.8 m/s (6 mph), gradually gaining strength through late spring, peaking at 4.8 m/s (11 mph) in May before tapering off. This December wind, though mild compared to the seasonal max, maintains a consistent flow, echoing the charming, crisp air that envelops the region as the year draws to a close.

Average December Wind Speed in Mill Valley

The chart displays monthly wind speed patterns in Mill Valley, with values for each month shown alongside December's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how December's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec2.83.43.64.14.84.43.83.53.13.22.23.2 m/s
Data source: Mill Valley December wind data, generated using information from the Copernicus Climate Change Service.

How December Weather in Mill Valley Compares to Other Months

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

In December, temperatures range from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), with an average temperature of 10°C (51°F). The month generally experiences 98 mm (3.9 in) of precipitation over approximately 9 days and maintains a humidity level of 79%. In contrast, January sees slightly cooler minimum temperatures dropping to 0°C (33°F) while the maximum reaches 23°C (73°F), with similar average temperatures of 10°C (51°F). The precipitation increases to 111 mm (4.4 in) across about 8 days, accompanied by a rise in humidity to 85%. For more details, you can check Mill Valley weather in January.

December and February showcase mild winter weather, though there are some notable differences. In December, temperatures range from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), with an average of 10°C (51°F). The month typically experiences 98 mm (3.9 in) of precipitation over about 9 days, accompanied by a humidity level of 79%. In contrast, February presents a slightly cooler minimum temperature of 2°C (35°F) and a marginally warmer average of 11°C (52°F), reaching up to 23°C (73°F) at its peak. Precipitation increases to 116 mm (4.6 in) over 8 days, with humidity rising to 82%. For more detailed information about weather patterns in February, you can check Mill Valley weather in February.

December and March exhibit noticeable differences in weather patterns. In December, temperatures range from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), with an average of 10°C (51°F) and substantial precipitation of 98 mm (3.9 in) over about 9 days, accompanied by a humidity level of 79%. In contrast, March sees a slight increase in temperatures, with a minimum of 4°C (39°F) and a maximum of 24°C (75°F), averaging 12°C (54°F). Precipitation in March is lower at 80 mm (3.1 in), spread over 10 days, and humidity rises slightly to 82%. For more specific insights, you can explore Mill Valley weather in March.

When comparing the weather in December and April, it’s clear that April tends to be warmer and drier. December boasts a cooler average temperature ranging from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), while April sees higher averages, with temperatures ranging from a minimum of 4°C (40°F) to a maximum of 28°C (83°F). Additionally, December experiences more precipitation, with 98 mm (3.9 in) over 9 days, compared to April's lighter 35 mm (1.4 in) over just 5 days. Despite similar humidity levels at 79%, April offers a more pleasant and sunny climate. For more detailed insights, you can refer to Mill Valley weather in April.

December weather in Mill Valley is characterized by a cooler climate, with temperatures ranging from a minimum of 3°C (38°F) to a maximum of 22°C (72°F) and an average of 10°C (51°F). The month sees considerable rainfall, averaging 98 mm (3.9 in) over about nine days, resulting in a humidity level of 79%. In contrast, May brings warmer temperatures, with a minimum of 7°C (45°F), an average of 15°C (60°F), and a maximum of 30°C (86°F). Precipitation drops significantly to just 20 mm (0.8 in) over two days, while humidity remains relatively high at 83%. For more details on May's weather, visit Mill Valley weather in May.

In December, the weather is significantly cooler, with average temperatures ranging from 3°C (38°F) to a maximum of 22°C (72°F), accompanied by a higher level of precipitation at 98 mm (3.9 in) over about 9 days. The humidity is fairly high at 79%, creating a damp atmosphere. In contrast, June offers a warmer climate, with temperatures ranging from a minimum of 10°C (51°F) to a maximum of 32°C (90°F). Notably, June experiences minimal precipitation at just 2 mm (0.1 in) over no rainy days, and humidity slightly increases to 84%. For a more detailed look at the conditions, check out Mill Valley weather in June.

December and July showcase contrasting weather patterns. In December, temperatures range from a cool minimum of 3°C (38°F) to a pleasant average of 10°C (51°F), peaking at a comfortable 22°C (72°F). This month also experiences significant precipitation, totaling 98 mm (3.9 in) spread over 9 days, accompanied by a humidity level of 79%. In stark contrast, July boasts a much warmer climate, with temperatures starting at a minimum of 11°C (52°F) and averaging 17°C (63°F), reaching a maximum of 30°C (87°F). Remarkably, July sees only 2 mm (0.1 in) of rainfall, with no rainy days, while the humidity level rises slightly to 87%. For more detailed insights on the hot summer days, check out Mill Valley weather in July.

When comparing the weather in December and August, notable differences emerge in both temperature and precipitation patterns. December experiences cooler temperatures, with a minimum of 3°C (38°F) and an average of 10°C (51°F), peaking at 22°C (72°F). Additionally, it is a wetter month, receiving 98 mm (3.9 in) of precipitation over 9 days, contributing to a humidity level of 79%. In contrast, August boasts warmer temperatures, ranging from a minimum of 11°C (52°F) to a maximum of 32°C (90°F), with a comfortable average of 18°C (64°F). It is notably dry, with just 1 mm (0.1 in) of precipitation over the entire month and no rainy days, accompanied by higher humidity at 87%. For a more detailed look at August weather, see Mill Valley weather in August.

In comparing the weather between December and September, December tends to be cooler and wetter. December's temperatures range from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), averaging around 10°C (51°F). In contrast, September features milder conditions, with a minimum of 9°C (49°F) and a maximum of 36°C (98°F), averaging 18°C (65°F). While December experiences approximately 98 mm (3.9 in) of precipitation over about 9 days, September is remarkably dry, receiving only 2 mm (0.1 in) without any rainy days. Humidity levels are also notable, with December at 79% and September slightly higher at 86%. For more detailed information on September weather, visit Mill Valley weather in September.

The weather in December contrasts significantly with that of October, showcasing a notable shift in temperatures and precipitation. In December, temperatures range from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), with an average of 10°C (51°F), reflecting a cooler climate overall. This month also experiences higher precipitation, averaging 98 mm (3.9 in) over 9 days, compared to October's milder conditions which feature a minimum of 6°C (44°F) and a maximum of 31°C (88°F), with an average of 16°C (62°F) and only 30 mm (1.2 in) of rain over just 2 days. The humidity remains relatively stable, around 79% in December and 80% in October. For more detailed insights into October's climate, you can check Mill Valley weather in October.

In comparing the weather between December and November, we see some notable differences. December experiences a lower average temperature of 10°C (51°F), compared to November's 13°C (55°F). While both months have the same minimum temperature of 3°C (37-38°F), November boasts a higher maximum temperature of 25°C (77°F) versus December's 22°C (72°F).

Precipitation also significantly increases in December, with 98 mm (3.9 in) falling over 9 days, compared to November's 48 mm (1.9 in) over just 5 days. However, humidity remains constant at 79% in both months. For more details on November's weather, you can visit Mill Valley weather in November.

Compare Mill Valley's Climate with Cities Worldwide

Conclusion: What to Expect From December Weather in Mill Valley

As December settles into Mill Valley, the weather takes on a distinct character that marks it as a transition from the milder, drier months. With a mix of cool temperatures averaging around 10°C (51°F) and occasional peaks reaching up to a pleasant 22°C (72°F), the month balances crisp air with bursts of warmth. This time of year also sees an increase in precipitation, bringing about a total of 98 mm (3.9 in) over approximately 9 days, resulting in an atmosphere that feels notably more humid—around 79%. These wet days contrast starkly with the drier conditions of previous months, immersing the town in a lush, revitalized landscape. For a comprehensive look at the seasonal variations, visit Mill Valley Climate.