Weather in Trieste in September

A good month. September works. It is not the peak, but nothing about it fights you. Highs average 24 °C, lows 16.6 °C, and rain falls on 11 days — nothing in the month is working against you.

September ranks 2 of 12 in Trieste. Only June scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain on 11 days, 4 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average September reaches 30 °C. Across the twenty years measured, the hottest September day reached 31.2 °C and the coldest night fell to 9.4 °C, and the wettest single day dropped 47 mm — roughly 42% of the month's rain in one day.

September is moderately variable: 38 mm in the driest year against 270 mm in the wettest, around an average of 113 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 7.6 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 71%.

How September sits in the year

The month is on the way down: 4.7 °C cooler than August, with October dropping another 4.8 °C. The first week and the last are not the same trip.

Daylight in September

12.6 hours of daylight, losing 1.6 hours across the month. That is between Trieste's extremes of 15.7 and 8.7 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 25.7 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Trieste versus nearby

If Trieste is one option among several, the nearby comparison is worth making. Villach is close enough to be a coin toss — 3.2 °C cooler, 2 days more rain. Padua is close enough to be a coin toss — within a degree on temperature, 1 day less rain.

So: September is effectively as good as it gets here — 1 points behind June, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Trieste

See all twelve months in Trieste, or where else to go in September.