Siena weather in September

Tuscany-forum regulars describe September in two halves: the first fortnight still properly warm, with late-summer storms that come from the heat and pass in a day or two, and the back end settling into the month people remember - one poster's late September ran 25C by day and 18C at night with nothing falling. Crowds are down from August without being gone; museums and restaurants still want booking. Two things to expect if you are here for the landscape rather than the towns: the wineries are flat out with the harvest, which makes formal tours harder to arrange, and by late September the fields are cut, so the hills are raked stubble rather than crops or sunflowers. The record for Siena: 24.8C days, 14.7C nights, 9.4 precipitation days carrying 93.4mm, 10.3 hours of sun.

Regulars are specific the Piazza del Campo turns wall-to-wall on the August 16th Palio race day itself, gates closing around 4pm ahead of a 5pm parade, though the day before is described as genuinely wonderful, Contradas marching the streets in full ceremonial dress without the crush. Our row backs that hot, genuinely dry read, 30.4C reading as a hot 31C, over 18.9C nights, with 45.2mm of rain across 7.1 days and humidity down to 61 percent. Regulars are consistent this counts as genuinely hot by day, accommodation with pool access or easy water nearby the standard recommendation for cooling off between sightseeing. This remains a real trade-off month, heat and Palio crowds against a once-a-year spectacle. The record: 12.3 hours of sun, a 12.7 kph wind and AQI 47.

July here has a fixed date in it: the Palio runs on the 2nd, and the board warns that the days either side are worse for crowds than the race day itself. Their description of the event is unromantic and useful - a medieval square, uneven and uncomfortable viewing space, packed full, and hot for everybody in it. Outside those days the city keeps a daily rhythm worth planning around: the coach day-trippers arrive about half past ten, the worst of it runs to around three, and by six the Campo is calm enough to sit out with a drink. Our row gives 30.3C reading as 32C at 60.4 percent humidity, over 18.7C nights, with almost no rain, 28.3mm across 5 days. The narrow lanes stay cool. The record: 13.3 hours of sun and AQI 45.

Italy-forum threads asking if March is a good month for travel (Siena specifically singled out as a favorite) land firmly on yes, especially for anyone who prefers a city without the crush of summer tourists. Posters describe days as genuinely pleasant, cool nights giving way to comfortable, often mild afternoons, though the standing advice is to stay flexible: duck into museums and churches when a wet spell rolls through, take advantage of the outdoor cafes on Piazza del Campo whenever the sun cooperates. March also happens to be peak season for white truffle hunting in the surrounding Tuscan countryside. Layering is essential regardless of the day's forecast, since even a warm afternoon can turn chilly fast once the sun starts dropping. The record: 13.8C days feeling like 11C, 3.8C nights, 72mm across 9.6 days, 0.4cm of late-season snowfall, 74 percent humidity and 9.2 hours of sun.

Siena regulars give May a split verdict and the arithmetic behind it is worth having. Mid-May to mid-September is the stretch to avoid if crowds are the priority, and May has been getting busier year on year. But the first days are the exception rather than the rule: Easter, the 25th of April and the 1st of May absorb the Italian holiday travel between them, so once past the 1st it settles down again until the summer proper, with children still in school. Their other note is that Siena thins out fast as you leave the centre for the contrade. The weather risk our row adds is water - 92.4mm across 13.2 precipitation days under a mild 20.8C is more than one wet day in three. The record: 10.6C nights, humidity 74 percent, 11.7 hours of sun and AQI 44.