Last updated: March 24, 2025
In Siena, Italy, September offers a delightful blend of warmth and mildness, with maximum temperatures reaching 32°C (90°F) and an average of 20°C (69°F). The charm of early autumn is accompanied by a bit of variability, as minimum temperatures can dip as low as 7°C (45°F). While savoring the stunning sights of this historic city, visitors should also anticipate about 84 mm (3.3 inches) of precipitation over approximately 9 days, ensuring pockets of refreshing rainfall amidst the sunshine. With a humidity level of 66%, September creates an inviting atmosphere, perfect for exploring Siena’s rich culture and vibrant surroundings.
In September, Siena ushers in a lovely transition from the intense summer heat to a more moderate climate, making it one of the most pleasant months to visit. With minimum temperatures around 7°C (45°F) and average highs peaking at 32°C (90°F), the days remain warm and inviting. This month strikes a harmonious balance as daytime temperatures encourage outdoor exploration, while the cooler evenings provide a refreshing respite. As summer fades and autumn subtly emerges, visitors can enjoy the city's stunning architecture and rich history against a backdrop of comfortably warm weather, perfect for leisurely strolls through its charming streets.
In September, Siena experiences a notable increase in precipitation, with 84 mm (3.3 in) of rain falling over 9 days. This marks a shift from the drier summer months of July and August, where rainfall dwindled to 38 mm (1.5 in) and 34 mm (1.3 in) respectively. The uptick in rainfall aligns with the onset of autumn, creating a vibrant landscape as the region prepares for the cooler, wetter months ahead. Not only does September set the stage for the lush greens of fall, but it also serves as a precursor to the even higher precipitation totals of 91 mm (3.6 in) expected in October and 148 mm (5.8 in) in November, signaling a transition into a wetter season.
In September, Siena experiences a modest increase in humidity, averaging around 66%. This marks a gentle transition from the drier summer months of July and August, where humidity dips to their lowest points at 57% and 55% respectively. As autumn approaches, the humidity levels begin to climb gradually, aligning with the arrival of cooler temperatures. This shift adds a touch of freshness to the air, contrasting with the sweltering summer, yet still remaining far below the high humidity levels common in the winter months of January and November, which soar to around 84%. September's humidity, therefore, strikes a pleasant balance, making it an ideal time to enjoy the beautiful landscapes and cultural richness of Siena.
As summer gently transitions into autumn, September in Siena, Italy, presents a notable shift in UV exposure. With a UV Index of 7, the month falls into the high exposure category, allowing for a burn time of 25 minutes. This marks a decrease from the peak of very high levels experienced in July and August, where sunseekers had to be particularly cautious. Interestingly, September's UV Index is on par with the earlier high of April, suggesting that while the days are getting shorter, the sun's rays remain potent. For those enjoying outdoor activities, it's essential to stay informed and protect your skin. To learn more about UV levels throughout the year, visit Siena UV Index.
UV Risk Categories
September in Siena, Italy, marks the transition from the sun-drenched heights of summer into the gentle embrace of autumn. With 335 hours of sunshine, the month reflects a notable decrease from the vibrant 432 hours of July and 402 hours of August, yet it still offers ample warmth and brightness. As summer fades, the golden light of September casts a unique charm over the historic city, illuminating its stunning Gothic architecture and lush landscapes. This lingering sunlight invites both locals and visitors to experience the city's enchanting ambiance, making it an ideal time for leisurely strolls through cobblestone streets and vibrant vineyards. As the sun begins to set earlier, Siena's evenings become a canvas for soft hues and a hint of autumn's arrival, paving the way for the seasonal changes ahead.
As September arrives in Siena, Italy, the likelihood of sunny weather presents a promising outlook, with a 55% chance of sunshine. This marks a notable shift from the summer peak months of July and August, which boast impressively high probabilities of clear skies at 64% and 66%, respectively. As the sun begins to fade into autumn, the sunny disposition of September still holds its own compared to the months preceding it, providing a delightful blend of warm days and slightly cooler evenings. Overall, it’s an inviting time to explore the enchanting streets of Siena, basking in the gentle sunlight that characterizes this transitional period.
As September arrives in Siena, Italy, the days begin a gentle transition, offering about 12 hours of daylight that heralds the onset of autumn. This month represents a midpoint in the gradual shift from the long, sun-drenched days of summer—where June boasts a generous 15 hours of daylight—to the shorter and cozier days of fall, with daylight dipping to 10 hours by October. Notably, September still enjoys longer days compared to the stark winter months, creating a comfortable balance that invites both locals and visitors to embrace the beautiful early autumn scenery. This gradual decrease in daylight not only enriches the landscape with vibrant fall colors but also signals a time for harvest and reflection in this picturesque Tuscan city.
In September, the wind in Siena, Italy, gently whispers a transition from the vibrant summer months to the crispness of autumn. With an average wind speed of 2.0 m/s (or 4 mph), September marks a noticeable decline from the breezier summer days, reflecting a calm before the seasonal shift. This mellow breeze is characteristic of the month, following a gradual decrease from August’s slightly brisk 2.1 m/s (5 mph). As we move into October, the winds pick up again, hinting at the refreshing autumn air to come. This serene yet shifting wind pattern encapsulates September's essence in Siena—a time of lingering warmth, soft breezes, and the anticipation of change.
The weather in Siena 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 Siena and find detailed weather information for every month.
September and January present contrasting weather experiences. In September, temperatures range from a comfortable 7°C (45°F) at night to a warm 32°C (90°F) during the day, with an average of around 20°C (69°F). This month experiences about 84 mm (3.3 in) of precipitation over 9 days, and the humidity is moderately high at 66%. In stark contrast, January brings much colder temperatures, with minimums dipping to -5°C (23°F) and daytime highs reaching only 15°C (59°F), averaging around 5°C (41°F). Precipitation in January is lower at 44 mm (1.7 in) over 7 days, but the humidity is notably higher at 84%. For more details on January weather, you can visit Siena weather in January.
In September, the weather is generally warm and pleasant, with temperatures ranging from a minimum of 7°C (45°F) to a maximum of 32°C (90°F), averaging around 20°C (69°F). This month experiences a relatively high humidity of 66% and sees about 84 mm (3.3 in) of precipitation over 9 days. In contrast, February brings much cooler temperatures, with minimums dropping to -5°C (23°F) and maximums reaching only 20°C (68°F), averaging at 7°C (46°F). The humidity is higher at 76%, and precipitation is slightly lower at 68 mm (2.7 in) over 8 days. For a closer look at the climate specifics for this month, check out Siena weather in February.
September and March showcase contrasting weather patterns, reflecting the transition between late summer and early spring. In September, temperatures range from a cool minimum of 7°C (45°F) to a warm average of 20°C (69°F), peaking at a high of 32°C (90°F). The month brings about 84 mm (3.3 in) of precipitation over approximately 9 days, with humidity levels hovering around 66%. In contrast, March sees much cooler temperatures, with a minimum of -11°C (12°F), an average of 9°C (49°F), and a maximum of 23°C (73°F). It experiences less precipitation, at 61 mm (2.4 in) across 8 days, with slightly higher humidity at 68%. For more detailed insights on March weather, you can check Siena weather in March.
In September, the weather tends to be warmer with average temperatures around 20°C (69°F) and highs reaching up to 32°C (90°F), while April sees cooler temperatures averaging 12°C (55°F) and maximums of 26°C (79°F). Both months experience similar levels of precipitation, with September receiving 84 mm (3.3 in) over 9 days and April slightly less at 81 mm (3.2 in) over 10 days. Humidity levels are somewhat comparable, but September is typically less humid at 66%, compared to April's 70%. For more detailed information on precipitation and temperature trends, you can check Siena weather in April.
In September, temperatures range from a minimum of 7°C (45°F) to a maximum of 32°C (90°F), with an average temperature of 20°C (69°F). The month sees about 84 mm (3.3 in) of precipitation over approximately 9 days, with humidity hovering around 66%. In contrast, May experiences cooler temperatures, with a minimum of 3°C (37°F) and an average of 16°C (62°F), while the maximum reaches 31°C (89°F). Precipitation is slightly higher at 91 mm (3.6 in), spread over about 13 days, and humidity is slightly elevated at 69%. Overall, September tends to be warmer and drier compared to the cooler and wetter May. For more details, visit Siena weather in May.
September and June weather present notable differences in temperature and precipitation. In September, the minimum temperature is slightly lower at 7°C (45°F), while the average stands at 20°C (69°F), with a maximum reaching up to 32°C (90°F). With 84 mm (3.3 in) of precipitation spread across 9 days, September tends to be wetter and more humid, with humidity levels at 66%. In contrast, June experiences milder temperatures, with a minimum of 9°C (49°F), an average of 22°C (71°F), and a maximum of 36°C (96°F). Additionally, June boasts significantly less precipitation at 38 mm (1.5 in) over just 6 days, accompanied by lower humidity of 62%. For more information on June weather, you can check Siena weather in June.
In comparing the weather of September and July, notable differences emerge in temperature and humidity. September experiences a wider range of temperatures, with a minimum of 7°C (45°F) and a maximum of 32°C (90°F), averaging around 20°C (69°F). In contrast, July is generally warmer, with minimum temperatures of 13°C (56°F) and maximums reaching 36°C (97°F), resulting in an average of 24°C (76°F). Humidity levels also differ, as September has a higher humidity of 66%, compared to July's 57%. Additionally, September tends to be wetter, with 84 mm (3.3 in) of precipitation over 9 days, while July sees less rain, amounting to 38 mm (1.5 in) over just 6 days. For those interested in the specifics, you can view the details at Siena weather in July.
September weather contrasts with August in several notable ways. While August enjoys a warmer average temperature of 25°C (77°F) with highs reaching up to 37°C (99°F), September cools down with an average of 20°C (69°F) and maximum temperatures of 32°C (90°F). Precipitation in September increases significantly, totaling 84 mm (3.3 in) over 9 days, compared to August's lighter rainfall of 34 mm (1.3 in) across just 5 days. Moreover, the humidity rises in September to 66%, up from August's 55%. For more detailed insights on August weather, visit Siena weather in August.
September and October present distinct shifts in weather patterns. In September, temperatures range from a minimum of 7°C (45°F) to a maximum of 32°C (90°F), averaging around 20°C (69°F), which offers warm days conducive to outdoor activities. However, with 84 mm (3.3 in) of precipitation over 9 days, humidity levels average at 66%, indicating a bit of mugginess. In contrast, October brings cooler conditions, with temperatures dipping to a minimum of 5°C (40°F) and averaging 15°C (59°F), peaking at 27°C (81°F). While October sees a slightly higher total precipitation of 91 mm (3.6 in) over just 8 days, the humidity increases to 79%, giving the month a more damp feel. For more detailed insights into October weather, you can check Siena weather in October.
September and November experience notable contrasts in weather. September boasts warmer temperatures, with averages around 20°C (69°F) and highs reaching up to 32°C (90°F), along with a relatively lower humidity of 66%. However, it sees moderate rainfall, totaling 84 mm (3.3 in) over about 9 days. In contrast, November brings a significant drop in temperatures, with averages plummeting to 11°C (51°F) and minimums dipping as low as -3°C (27°F). This month also experiences increased precipitation, with 148 mm (5.8 in) spread over approximately 15 days, and higher humidity at 84%. For more specifics on November weather, you can check Siena weather in November.
September weather is generally warm and pleasant, with average temperatures around 20°C (69°F) and highs reaching up to 32°C (90°F). The month receives about 84 mm (3.3 in) of precipitation over approximately 9 days, accompanied by a humidity level of 66%. In contrast, December presents a much cooler climate, featuring average temperatures of 7°C (44°F) and maximums of only 16°C (61°F). Precipitation slightly increases to 98 mm (3.8 in) over 11 days, coupled with higher humidity at 83%. For more details on the December climate, you can check Siena weather in December.
As September rolls into Siena, the weather begins to show a delightful shift from the sweltering summer heat, offering a pleasant combination of comfortable temperatures and a touch of autumn’s embrace. With an average temperature around 20°C (69°F), visitors can enjoy the city's rich culture in a more temperate climate, unlike the scorching days of July and August. While occasional rain may occur—averaging about 9 days of precipitation—it contrasts the drier summer months, adding a refreshing atmosphere to the landscape. As the humidity settles at 66%, it’s the perfect time for exploring Siena's historic streets. For a deeper insight into the changing conditions, check out Siena Climate.