Monthly climate guide
Siena weather in September
With highs near 27°C (80°F) and lows around 14°C (58°F), September feels warm in Siena. Rainfall averages about 60 mm (some rain) and the sky is a mix of sun and cloud. Daytime highs are 6°C cooler than August and 6°C warmer than October.
What stands out in September
- Evenings cool off sharply: the daily range is around 12°C, so pack a layer.
- In Siena, September is early autumn.
- Siena is usually about 3°C warmer than Florence, 50 km away, in September.
- Temperatures are falling — expect highs around 6°C lower by October.
Avg high
27°C
80°F
Avg low
14°C
58°F
Rainfall
60 mm
some rain
Humidity
66%
relative
Sky
47%
cloud · a mix of sun and cloud
Siena weather by month
Show the monthly averages as a table
| Month | Avg high | Avg low | Rain | Humidity | Cloud cover |
|---|---|---|---|---|---|
| January | 9°C / 48°F | 1°C / 34°F | 54 mm | 88% | 65% |
| February | 10°C / 50°F | 1°C / 34°F | 72 mm | 85% | 64% |
| March | 14°C / 57°F | 4°C / 38°F | 69 mm | 80% | 58% |
| April | 18°C / 65°F | 7°C / 44°F | 53 mm | 76% | 60% |
| May | 22°C / 71°F | 10°C / 50°F | 61 mm | 71% | 61% |
| June | 28°C / 83°F | 15°C / 59°F | 37 mm | 61% | 41% |
| July | 32°C / 90°F | 18°C / 65°F | 37 mm | 55% | 30% |
| August | 33°C / 91°F | 18°C / 65°F | 33 mm | 55% | 28% |
| September | 27°C / 80°F | 14°C / 58°F | 60 mm | 66% | 47% |
| October | 21°C / 70°F | 10°C / 50°F | 84 mm | 77% | 56% |
| November | 15°C / 58°F | 6°C / 43°F | 100 mm | 87% | 66% |
| December | 11°C / 51°F | 2°C / 36°F | 64 mm | 89% | 61% |
What to pack for September
- T-shirts plus a light layer for the evening
- Comfortable trainers or sandals for long walks
- An extra layer — evenings are noticeably cooler than afternoons
- A small travel umbrella, just in case
Is September a good time to visit Siena?
Compare the months in the chart above to find your ideal window.
Best time to visit Siena →Other Italy cities in September
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Siena weather in September. WeatherCompare, 2026 (NASA POWER / ERA5, 2011–2020 monthly averages). https://weathercompare.eu/weather/italy/siena/september
<a href="https://weathercompare.eu/weather/italy/siena/september">Siena weather in September</a> (WeatherCompare)
<iframe src="https://weathercompare.eu/embed/italy/siena" width="300" height="160" style="border:0;border-radius:12px" loading="lazy" title="Siena weather in September"></iframe> <p style="font-size:12px"><a href="https://weathercompare.eu/weather/italy/siena/september">Siena weather in September</a> – WeatherCompare</p>
Siena in September: quick answers
Is September a good time to visit Siena?
September is a reasonable time for Siena: highs around 27°C and about 60 mm of rain, though not one of the three best months.
How warm is Siena in September?
Average highs are about 27°C (80°F) and average lows about 14°C (58°F), based on 10 years of daily data.
Does it rain a lot in Siena in September?
Siena typically gets around 60 mm of rain in September — some rain.
Figures are long-term averages for the area around Siena (NASA POWER / ERA5, 2011–2020), not a forecast for a specific year. For upcoming days, see the live multi-source forecast.