Last updated: February 24, 2025
In September, Half Moon Bay experiences a delightful transition into autumn, with maximum temperatures reaching up to 31°C (88°F) and an average hovering around 16°C (62°F). Nights bring a comfortable chill, with minimums dipping to 11°C (52°F). This month enjoys a dry streak, boasting only 3 mm (0.1 in) of precipitation across zero rainy days, making it an ideal time for outdoor activities. With an elevated humidity level of 86%, the coastal climate remains pleasantly refreshing, inviting both residents and visitors to revel in the beauty of this picturesque coastal town.
As summer transitions to fall, Half Moon Bay experiences a delightful shift in temperatures throughout September. With minimums around 11°C (52°F), the crisp mornings give way to pleasantly warmer days, peaking at a stunning 31°C (88°F). This month showcases an average temperature of 16°C (62°F), making it one of the warmer periods of the year, characterized by a striking range that highlights the coastal charm of the area. Notably, September is warmer than the preceding months, reflecting a pattern where late summer warmth lingers just a bit longer before the cooler autumn breezes set in. It's a perfect time for outdoor adventures, as the weather invites both locals and visitors to bask in the golden sunlight and enjoy the stunning coastal scenery.
In September, Half Moon Bay experiences a remarkable transition towards drier weather, with only 3 mm (0.1 in) of precipitation recorded throughout the month. This minimal rainfall continues the trend seen since early summer, where June, July, and August each reported virtually no rainfall at all. With zero precipitation days in September, residents and visitors alike enjoy clear skies and pleasant temperatures, setting the stage for the upcoming months. As autumn begins, October brings a slight uptick in precipitation, but September stands out as a month of notable dryness in a year where winter rainfall remains significantly higher, particularly in the preceding and following months.
September in Half Moon Bay, United States, witnesses a slight dip in humidity compared to the peak summer months, recording an average of 86%. This skirts just below the heights of 87% seen in both July and August, suggesting that while summer’s humidity lingers, the onset of autumn brings a subtle relief. The trend throughout the year shows a gradual decrease from the humid heights of summer, beginning to stabilize as the temperatures cool down toward October’s 80%. Notably, the overall pattern reveals high humidity levels predominantly during the summer months, while the fall and winter settle into more moderate figures, making September a transitional month in the coastal climate.
In September, Half Moon Bay experiences a UV Index of 9, placing it firmly within the very high exposure category, with a burn time of just 15 minutes. This trend continues the pattern established throughout the summer months, where UV Index levels peaked at 11 in July and June. As the seasons transition, the UV Index begins to decline from its summer highs, yet remains significant enough to warrant caution. Sun safety remains essential, as even the slight decrease from August's 10 underscores the potential for skin damage on sunny days. To stay informed about UV levels this September and beyond, check out the detailed resource at Half Moon Bay UV Index.
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As summer transitions into autumn, September in Half Moon Bay enjoys a generous 299 hours of sunshine, making it one of the sunniest months of the year. This slight dip from the vibrant August, which boasts 320 hours, reflects a typical trend where sunshine begins to wane as the days grow shorter. The month serves as a perfect bridge, showcasing warm days and cool breezes, while inviting residents and visitors alike to relish the beauty of nature before the close of summer. With sunshine hours steadily increasing from the 151 hours in January to a peak in June's 355 hours, September's light is a cherished reminder of the sunny summer days, setting the stage for the more subdued fall months ahead.
In Half Moon Bay, September offers a pleasant balance of sun, with a 47% chance of clear skies, making it one of the sunnier months of the year. As summer winds down, the likelihood of sunshine slightly improves compared to the preceding months, such as July and August, which dip to 30% and 43% respectively. The trend shows a gradual recovery in sun potential as the year moves towards autumn, though it doesn't completely rise above the 50% mark until October. This makes September an appealing time for outdoor activities, as visitors can enjoy the lingering warmth while still seizing the opportunities for sunny days in the beautiful coastal landscape.
As summer fades into autumn, September in Half Moon Bay brings a gentle shift in daylight duration, with an average of 12 hours of light. This gradual decrease marks the transition from the peak summer months, where daylight reached its maximum at 14 hours in both June and July. Following the warmth of August's 13-hour days, September signals a soft retreat, leading into October's shorter 11-hour days. The trend through the year showcases a clear rhythm, with longer, sun-filled days in the spring and summer giving way to shorter, cozier hours of sunlight as the year progresses towards winter. This natural ebb and flow of daylight not only influences the local atmosphere but also sets the stage for the seasonal changes ahead.
In Half Moon Bay during September, the average wind speed gently drifts down to 3.1 m/s (7 mph), marking a notable decline as summer wanes. This decrease is consistent with the overall trend seen throughout late summer; July and August also experienced lower winds, at 3.4 m/s (8 mph) and 3.3 m/s (7 mph), respectively. As the vibrant energy of summer subsides, the calming breezes of early autumn invite a reflective ambiance. Yet, winds begin to pick up again in October, hinting at the seasonal shift ahead, where the gusts will typically range back to 3.8 m/s (9 mph). This rhythmic ebb and flow of winds beautifully encapsulates the transition from warm summer days to the cooler, more invigorating autumn air in this picturesque coastal town.
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 September'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.
September and January present contrasting weather patterns. In September, temperatures range from a mild minimum of 11°C (52°F) to a warm maximum of 31°C (88°F), with an average of 16°C (62°F) and minimal precipitation of just 3 mm (0.1 in) over no rainy days, complemented by high humidity at 86%. In stark contrast, January is much cooler, with temperatures dipping to a minimum of 5°C (41°F) and peaking at only 20°C (68°F), averaging 11°C (53°F). This month experiences significantly more rainfall, totaling 102 mm (4.0 in) over 9 days, while maintaining a humidity level slightly lower at 85%. For a more detailed perspective on January weather, check out Half Moon Bay weather in January.
September and February present markedly different weather patterns. In September, temperatures range from a minimum of 11°C (52°F) to a maximum of 31°C (88°F), with an average of 16°C (62°F). This month experiences minimal rainfall, with only 3 mm (0.1 in) of precipitation and no rainy days, along with high humidity at 86%. In contrast, February is cooler, with temperatures ranging from 5°C (41°F) to 20°C (69°F) and an average of 11°C (53°F). This month is significantly wetter, receiving 101 mm (4.0 in) of precipitation over 9 days, while humidity is slightly lower at 82%. For more specific details about February weather, you can refer to Half Moon Bay weather in February.
Comparing the weather in September and March reveals notable differences in temperature and precipitation. September typically enjoys warmer temperatures, with a minimum of 11°C (52°F) and a maximum reaching 31°C (88°F), creating an average of 16°C (62°F). In contrast, March experiences cooler conditions, with a minimum of 7°C (44°F) and a maximum of 19°C (67°F), leading to a lower average of 12°C (53°F). Additionally, September is characterized by very little precipitation, averaging only 3 mm (0.1 in) over 0 days, while March is much wetter, recording 77 mm (3.0 in) of rainfall over 11 days. Both months have high humidity levels, but September has a slightly higher average of 86% compared to March's 82%. For more details on March weather, check out Half Moon Bay weather in March.
When comparing the weather in September and April, it's clear that September enjoys warmer temperatures, with a minimum of 11°C (52°F) and an average of 16°C (62°F), peaking at a comfortable 31°C (88°F). In contrast, April is generally cooler, with temperatures ranging from a minimum of 7°C (45°F) to a maximum of 25°C (78°F) and an average of 12°C (55°F). September also boasts significantly lower precipitation, with just 3 mm (0.1 in) recorded on 0 days, while April experiences more rainfall at 34 mm (1.3 in) spread over 5 days. Humidity levels remain relatively high in both months, but September is slightly more humid at 86% compared to April's 79%. For a detailed look at the weather in April, you can check Half Moon Bay weather in April.
When comparing the weather in September and May, notable differences emerge. September experiences warmer temperatures, with a minimum of 11°C (52°F), an average of 16°C (62°F), and a maximum of 31°C (88°F). In contrast, May tends to be cooler, showcasing a minimum of 9°C (48°F), an average of 13°C (56°F), and a maximum of 21°C (69°F). Additionally, September is quite dry, receiving only 3 mm (0.1 in) of precipitation over zero days, while May sees more rain, with 22 mm (0.9 in) spread across two days. Humidity remains relatively high in both months, with September at 86% and May slightly lower at 83%. For more detailed climate insights, you can check Half Moon Bay weather in May.
In comparing the weather of September and June, both months exhibit mild temperatures, but September tends to be warmer overall. In September, the minimum temperature is 11°C (52°F), with averages reaching up to 16°C (62°F) and a maximum of 31°C (88°F), while June has slightly cooler temperatures, ranging from a minimum of 10°C (51°F) to a maximum of 27°C (81°F). Precipitation is minimal in both months, with September receiving 3 mm and June slightly higher at 4 mm, but neither month experiences any rainy days. Humidity levels are comparable, with September at 86% and June at 84%. For more detailed information on June weather specifics, you can visit Half Moon Bay weather in June.
In comparing the weather of September and July, September features a broader temperature range, with minimums at 11°C (52°F), averaging 16°C (62°F), and maximums soaring to 31°C (88°F). In contrast, July maintains cooler temperatures, with a minimum of 11°C (51°F), an average of 15°C (59°F), and peaks at just 20°C (69°F). Both months experience minimal rainfall, each recording only 3 mm (0.1 in) with no rainy days, while humidity levels are quite comparable, hovering around 86% in September and 87% in July. For a more detailed look at July's weather, you can view Half Moon Bay weather in July.
In comparing the weather between August and September, we notice a notable increase in maximum temperature, with September reaching up to 31°C (88°F) compared to August's peak of 24°C (76°F). Both months share similar minimum temperatures, hovering around 11°C (52-53°F) and average temperatures are relatively close at 16°C (61-62°F). Furthermore, neither month recorded any precipitation, as both experienced dry conditions with just 3 mm (0.1 in) of rain. However, humidity levels slightly decrease in September to 86% from August's 87%. For more details on August weather, visit Half Moon Bay weather in August.
September typically enjoys warmer temperatures, with daily highs reaching up to 31°C (88°F) and a pleasant average of 16°C (62°F). The month is characterized by minimal precipitation, averaging just 3 mm (0.1 in) and experiencing no rainy days, alongside relatively high humidity at 86%. In contrast, October sees a slight drop in temperatures, with maximums around 27°C (80°F) and an average of 15°C (60°F). This month also brings increased rainfall, totaling 27 mm (1.1 in) across two days, while humidity decreases slightly to 80%. For more details on what to expect, check out Half Moon Bay weather in October.
September typically offers warmer weather, with average temperatures around 16°C (62°F) and maximums reaching up to 31°C (88°F). The month is quite dry, with only 3 mm of precipitation over zero rainy days and a high humidity level of 86%. In contrast, November brings cooler temperatures, averaging 13°C (56°F) and peaking at 21°C (70°F). This month sees more precipitation, totaling 48 mm (1.9 in) over five days, alongside a decrease in humidity at 79%. For more detailed insights, you can refer to Half Moon Bay weather in November.
September weather is characterized by warmer temperatures, with a minimum of 11°C (52°F) and an average high of 31°C (88°F), making it a pleasant time for outdoor activities. In contrast, December sees a noticeable drop in temperatures, with a minimum of 6°C (44°F) and a maximum of 19°C (67°F), creating a significantly cooler atmosphere. Additionally, September boasts minimal precipitation with only 3 mm over 0 days, while December experiences much wetter conditions, receiving 92 mm of rain over 10 days, contributing to a more humid but less humid environment at 79%. For more detailed insights, you can refer to Half Moon Bay weather in December.
As summer transitions into fall, September in Half Moon Bay offers a delightful reprieve from the heat, characterized by warm temperatures that occasionally peak around 31°C (88°F). The average daytime warmth allows for comfortable outdoor activities, while chilly evenings beckon cozy layers. Notably, September stands out with its lack of rainfall, featuring no precipitation days, which is a stark contrast to the wetter months that precede it. The high humidity of 86% adds a touch of richness to the air, enhancing the beauty of this coastal gem. For those looking to plan ahead, understanding the nuances of the seasonal shifts is key; discover more insights here: Half Moon Bay Climate.