Last updated: February 24, 2025
In Boulder, Colorado, December ushers in a crisp winter ambiance with an average temperature of -2°C (29°F), where maximums reach up to 19°C (67°F) on milder days, and minimums plunge to a chilly -19°C (-1°F). This month experiences 19 mm (0.8 in) of precipitation spread over approximately 4 days, contributing to the region's 89% humidity levels, creating a vibrant yet frosty atmosphere. The blend of varying temperatures and moisture makes December in Boulder a unique experience, perfect for winter enthusiasts.
In December, Boulder, United States, experiences a sharp chill as temperatures dip, with minimums around -19°C (-1°F) and an average of -2°C (29°F). While the cold can be biting, it's tempered with maximum daytime highs reaching 19°C (67°F), providing brief moments of warmth amidst the frosty landscape. This pattern reflects a trend as winter settles in, with temperatures considerably lower than the preceding months. As the year draws to a close, residents and visitors alike can expect a transition into the heart of winter, marked by its unique charm and the potential for snow-covered adventures.
December brings a gentle close to Boulder’s precipitation patterns, with only 19 mm (0.8 in) of rain over a brief 4 days. This drop in rainfall marks a trend towards the drier winter months, as temperatures cool and the holiday season approaches. Compared to the wetter spring, where May peaks at 134 mm (5.3 in) across 16 days, December’s precipitation is a stark contrast, showcasing Boulder’s transition into a drier, more serene season. As the year wraps up, residents can expect crisp air and clear skies, setting the stage for snow-capped peaks and the serenity of winter.
As December rolls into Boulder, the city experiences a notable uptick in humidity, reaching 89%, which is the highest for the year. This increase contrasts sharply with the drier months of July and August, where humidity hovered around 52-56%, bringing about a more refreshing feel. As we transition from the warm summer months into late autumn, humidity steadily rises, peaking after a slight dip in October. November closes out fall with an 82% humidity level, setting the stage for December's damp embrace. This seasonal shift not only influences the climate but also adds a crispness to the air, making the snowy landscape all the more enchanting during the holiday season.
In December, Boulder experiences a moderate UV Index of 4, similar to January's levels, indicating that while sun exposure is generally safe, caution is still advisable during peak hours. The burn time remains relatively lengthy at 30 minutes, suggesting that with appropriate protection, outdoor activities can be enjoyed without significant risk. As the year progresses, there's a notable trend of increasing UV intensity from January through August, peaking at 12 during the summer months when the exposure category shifts to extreme. This cyclical pattern highlights the importance of vigilant sun safety practices as UV levels rise, particularly in late spring and summer. For more details, check the comprehensive guide at Boulder UV Index.
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In December, Boulder basks in an average of 238 hours of sunshine, a delightful continuation of the year’s bright trend but noticeably lower than the sunnier months preceding it. As the calendar approaches the year’s end, daylight begins to wane, following the peak of July's 378 hours. This gradual decline highlights December's position in the sunniest season, with 237 hours of sunshine in February marking the transitional point toward longer days. Despite the winter chill, December still offers a generous amount of radiant days, inviting residents and visitors to enjoy the crisp air and stunning views of snow-capped mountains under a brilliant sky.
In Boulder, the likelihood of sunny weather in December is notably high at 68%, positioning it as one of the sunniest months of the year. This trend reflects a significant increase from the preceding months, particularly when compared to the lower probabilities of sunshine in the spring and early summer. While the summer months peak in sun exposure, December stands out as a gateway into winter, offering a pleasant surprise with its relatively bright skies. As the year wraps up, Boulderites can cherish the sun-drenched days amidst the chill, making December a delightful month for outdoor activities and seasonal festivities.
As the year draws to a close in Boulder, daylight hours dip to 9 hours in December, mirroring the limited light of November. This trend highlights a consistent seasonal fluctuation where shorter days prevail in the winter months. Following December, daylight begins to gradually increase, suggesting an upward trajectory as the days lengthen from January's 9 hours to February's 10 hours. The pattern reveals a smooth transition from the darker days of winter to the vibrant, longer daylight periods that characterize the spring and summer months. This rhythmic shift underscores the natural ebb and flow of daylight throughout the year, offering a glimpse into the changing seasons in Boulder.
In Boulder, United States, the December winds take on a brisk character, averaging 3.0 m/s (7 mph), marking a notable increase as winter settles in. This uptick follows a gradual rise in wind speed from 2.9 m/s (6 mph) in November, suggesting a trend where the end of the year brings more spirited breezes to the region. As the seasons shift, December's winds contrast with the milder, more variable speeds seen earlier in the year; for instance, summer months like July and August typically hover around 2.1 m/s (5 mph). The gradual increase in wind speed culminates in December, reflecting a seasonal transition that many Boulder residents eagerly anticipate, perfect for winter activities amidst the picturesque mountain backdrop.
The weather in Boulder 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 Boulder and find detailed weather information for every month.
In December, temperatures in Boulder range from a minimum of -19°C (-1°F) to a maximum of 19°C (67°F), with an average of -2°C (29°F). The month experiences relatively light precipitation, totaling 19 mm (0.8 in) over just four days, while humidity remains high at 89%. In contrast, January sees colder conditions, with temperatures dipping lower, where the minimum reaches -24°C (-12°F) and the average drops slightly to -3°C (26°F). Despite these cooler days, the maximum temperature is 15°C (59°F). Precipitation increases to 25 mm (1.0 in) spread over five days, and humidity is slightly lower at 88%. For more detailed insights into January's weather, you can check Boulder weather in January.
In December, the weather exhibits a milder range with average temperatures around -2°C (29°F) and occasional highs reaching up to 19°C (67°F). The month sees relatively low precipitation, averaging 19 mm (0.8 in) over four days, alongside a high humidity level of 89%. In contrast, February tends to be colder, with an average temperature of -4°C (26°F) and lows dropping to -26°C (-14°F). This month also experiences increased precipitation, totaling 36 mm (1.4 in) over nine days, and humidity remains slightly lower at 87%. For more details on February weather, you can check out Boulder weather in February.
December and March present contrasting weather conditions as the year transitions from winter to early spring. December experiences milder temperatures, with averages around -2°C (29°F) and a maximum reaching 19°C (67°F), although it can drop to as low as -19°C (-1°F). In contrast, March tends to be colder, with minimum temperatures of -21°C (-5°F) and averages slightly above freezing at 2°C (35°F). Precipitation is more prevalent in March, accumulating to 62 mm (2.5 in) over 11 days, compared to December's 19 mm (0.8 in) over just 4 days. Overall, while December maintains a higher humidity of 89%, March’s humidity stands at a lower 81%, indicating a shift in weather patterns as the seasons change. For more details, check out Boulder weather in March.
December and April present contrasting weather patterns. In December, temperatures can plummet to a minimum of -19°C (-1°F), with an average of -2°C (29°F) and a maximum of 19°C (67°F), while the month sees minimal precipitation (19 mm) over just four days. This leads to a high humidity level of 89%, contributing to a cold and crisp atmosphere. In contrast, April experiences a milder climate with a minimum temperature of -17°C (2°F) and an average of 5°C (42°F), peaking at 24°C (75°F). Precipitation significantly increases to 68 mm over 12 days, and humidity drops to 76%, creating a more variable and often wetter environment typical of spring. For more detailed weather insights, check out Boulder weather in April.
December and May present striking contrasts in weather patterns. In December, temperatures can plummet to a minimum of -19°C (-1°F), with an average of -2°C (29°F) and a maximum reaching 19°C (67°F). Precipitation is relatively low, occurring on just 4 days and totaling 19 mm (0.8 in), accompanied by high humidity at 89%. In contrast, May boasts milder conditions, with a minimum temperature of -9°C (17°F) and an average of 10°C (50°F) to a much warmer maximum of 27°C (81°F). However, May experiences significantly more rainfall, accumulating 134 mm (5.3 in) over 16 days, while the humidity drops to 66%. For more details about weather in this month, check out Boulder weather in May.
December and June present stark contrasts in weather conditions. In December, temperatures typically hover around a chilly average of -2°C (29°F), with minimums plunging to -19°C (-1°F) and occasional peaks of 19°C (67°F). The month experiences a high humidity level of 89%, along with light precipitation on about 4 days, totaling 19 mm (0.8 in). In contrast, June brings milder temperatures, with an average of 17°C (63°F) and maximums reaching a sweltering 34°C (93°F). The humidity drops to a more comfortable 58%, but the month also sees increased precipitation, averaging 74 mm (2.9 in) over 14 days. For a detailed look at Boulder’s June weather, check this link: Boulder weather in June.
December and July present stark contrasts in weather conditions. December's temperatures can plummet as low as -19°C (-1°F), with an average around -2°C (29°F) and highs reaching 19°C (67°F). The month sees modest precipitation of 19 mm (0.8 in) over four days, coupled with high humidity at 89%. In contrast, July offers much warmer temperatures, with a minimum of 7°C (45°F), an average of 20°C (68°F), and maximums soaring to 34°C (93°F). This summer month experiences significantly higher precipitation at 71 mm (2.8 in) spread over 16 days, and relative humidity drops to a more comfortable 52%. For a detailed look at Boulder’s weather during the warmer months, check out Boulder weather in July.
December and August exhibit stark contrasts in weather patterns. In December, temperatures can plunge as low as -19°C (-1°F), with an average temperature around -2°C (29°F) and a maximum of 19°C (67°F). This month experiences relatively low precipitation, with only 19 mm (0.8 in) and humidity levels soaring at 89%. In contrast, August boasts milder temperatures, ranging from a minimum of 7°C (45°F) to a comfortable average of 19°C (67°F) and a peak of 33°C (91°F). Precipitation increases significantly during this month, totaling 67 mm (2.7 in) over 13 days, while humidity drops to a more manageable 56%. For more detailed information on August weather, check out Boulder weather in August.
December and September present strikingly different weather conditions. In December, temperatures can drop as low as -19°C (-1°F), with an average around -2°C (29°F) and a maximum of 19°C (67°F). The month experiences high humidity levels at 89%, but only sees about 19 mm (0.8 in) of precipitation over 4 days. In contrast, September boasts a milder climate, with temperatures ranging from a minimum of -4°C (25°F) to a maximum of 33°C (92°F) and an average of 16°C (61°F). It also experiences greater precipitation at 42 mm (1.6 in) spread over 8 days, accompanied by a more comfortable humidity level of 65%. For more details on September weather, you can visit Boulder weather in September.
In comparing December and October weather, December tends to be colder overall, with average temperatures around -2°C (29°F) compared to October's milder average of 7°C (45°F). While both months experience chills, October sees a lower minimum temperature of -20°C (-5°F), signaling the onset of winter. Precipitation levels are notably higher in October, with 48 mm (1.9 in) over 7 days, whereas December experiences just 19 mm (0.8 in) across 4 days. Furthermore, December's humidity is higher at 89% compared to October's 76%, indicating a more damp and wintry atmosphere. For more details on October conditions, you can visit Boulder weather in October.
In comparing the weather of December to November, December experiences a notable drop in average temperature, with a minimum of -19°C (-1°F) and an average of -2°C (29°F) compared to November's minimum of -16°C (3°F) and average of 2°C (36°F). While both months see some warmth, December's maximum temperature reaches 19°C (67°F), slightly below November's peak of 22°C (71°F). Precipitation in December is somewhat lighter at 19 mm (0.8 in) over 4 days, whereas November has higher precipitation levels at 30 mm (1.2 in) over 6 days. Additionally, December's humidity is slightly higher at 89% compared to November's 82%. For more insights into November's weather, you can check out Boulder weather in November.
As December unfolds in Boulder, the weather paints a dramatic contrast to the milder months that precede it. With a chilling average temperature of -2°C (29°F), this month ushers in winter's embrace, showcasing its coldest days, where lows can plummet to -19°C (-1°F). While precipitation is relatively sparse, with only 19 mm spread across 4 days, the high humidity of 89% adds to the brisk atmosphere, creating that signature wintry feel. For those curious about Boulder's distinct climate throughout the year, explore more at Boulder Climate.