May to mid June, or September into mid October. That is the answer, it is not particularly close, and the rest of this guide is really an explanation of why.
Ostuni has a specific problem that shapes the whole question of timing: it is a small white town on a hot hill, seven kilometres from a coast that is at its best in high summer. So the months when the sea is most inviting are exactly the months when the town is least pleasant, and the trick is finding the overlap.
Shoulder season, and why it wins
The overlap is September, and to a slightly lesser extent late May and early June.
In September the sea is still holding the summer, sitting comfortably in the mid twenties, while the land has begun to let go of it. The light lengthens and softens, which matters enormously in a town made entirely of white surfaces. The restaurants are all still open, the boats are still running, and the crowds thin week by week. By late September and into early October you get the town back.
May into mid June is the other window. Everything is open, the whitewash has usually been refreshed and is at its brightest, the countryside is green rather than burnt, and there are far fewer people. The catch is the sea, which does not really warm up until the end of May and will feel cold to most people before then. Come in May for the town and the landscape rather than for swimming.
Month by month
January and February. Cold by Mediterranean standards, with daytime temperatures around 13C, and January the coldest month at about 10C on average. The sea bottoms out near 13C in February. Much of the seasonal town is closed. Beautiful, empty, and not a beach holiday.
March and April. The town wakes up. Cool mornings that need a jacket, mild afternoons that let you sit outside for a coffee. The countryside is at its greenest and the light is clean. Sea still too cold for most people. Some seasonal restaurants and beach operations are not open yet, which is the trade-off.
May. One of the two best months. Warm, dry, bright, thin crowds. The sea becomes swimmable toward the end of the month if you are not fussy.
June. Excellent up to about the middle. Warm sea, long days, everything open, and the crowds still manageable. From late June it starts filling.
July. Hot and busy. Average highs around 30C. The sea is lovely at roughly 24C to 26C. The town in the middle of the day is hard work.
August. The hottest and fullest month. Highs average about 30.6C with lows around 23.6C, and the heat index pushes past 33C. The sea peaks at about 26C, which is genuinely the best swimming of the year. But restaurant tables are hard to get, the beaches are packed and the old town at two in the afternoon is an endurance exercise. Italian holidays fall this month and the whole country moves to the coast.
September. The best month overall. Warm sea, softening light, everything open, crowds falling away through the month.
October. Quiet and lovely into the middle of the month, with the sea still swimmable early on and the town returning to itself. By late October things start closing.
November and December. Wet and quiet. Worth it if you want the white lanes entirely to yourself and do not mind that half the restaurants are shut.
If you can only come in August
Plenty of people can only travel then, so here is how to make it work.
Move your day to the edges. Be in the old town before nine and after seven, and treat eleven until five as time to be at the coast or somewhere with thick walls and a shuttered window. This is what people who live here do and it is not a compromise, it is the correct way to use a Puglian summer day.
Book everything. Restaurants several days ahead, accommodation months ahead.
And strongly consider a masseria rather than a room in town, because a pool in the middle of an August afternoon changes the entire holiday.
What is open when
The other half of the timing question is not weather but whether anything is running.
Ostuni’s old town lives year round, so the core of it, the lanes, the cathedral, the everyday bars and a decent number of restaurants, is open whenever you come. What is seasonal is everything attached to the coast and to tourism: the beach lidos, the boat operators, some of the terrace restaurants at the edge of the walls, and a proportion of the smaller guesthouses.
Broadly, the coastal season runs from around May to early October, with everything fully open from June through September. Come in March and the town is lovely and the beaches are shut. Come in November and a noticeable share of the restaurants you read about will be closed for the month.
Masserie are the exception worth planning around: many out on the plain close for a stretch of the winter entirely, so if a specific estate is the reason you are going, check its season before you book flights.
The one thing to check before you book
Sea temperature and air temperature do not move together. The sea lags the land by about two months, which is why September swimming is better than June swimming even though June feels hotter on shore. If the water is the reason you are coming, September beats May every time.
Frequently Asked Questions
What is the best month to visit Ostuni?
September. The sea is still warm at around 24C to 26C, the light has softened, everything is open and the summer crowds are thinning through the month. May is the best alternative if you care more about the town and the countryside than about swimming.
How hot does Ostuni get in summer?
August averages highs of about 30.6C with lows around 23.6C, and the heat index can reach roughly 33C. July is close behind at around 30C. The old town, being white stone on a hill, is very bright and very hot in the middle of the day.
When is the sea warm enough to swim near Ostuni?
July through September, when it sits between about 24C and 26C, peaking around 26C in August. June is borderline. By February the sea drops to about 13C.
Is Ostuni worth visiting in winter?
Yes, if you know what you are getting. Daytime temperatures sit around 13C, the lanes are empty and the light on the whitewash is beautiful. But a good part of the seasonal town is shut and swimming is out of the question. Come for the place, not for a holiday.
How busy is Ostuni in August?
Very. It is the peak of both the international and the Italian holiday season, restaurant tables need booking days ahead, the beaches fill early and the old town is congested through the middle of the day. If August is your only option, use the early mornings and the evenings and stay somewhere with a pool.
Read also: the best beaches near Ostuni, staying in a masseria near Ostuni, and the complete guide to Ostuni.
