Weather in Sydney in September

A good month. September is a solid month to be in Sydney. Highs average 19.1 °C, lows 13 °C, and rain falls on 12 days — nothing in the month is working against you.

September ranks 3 of 12 in Sydney. Only July scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain on 12 days, 3 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 29.1 °C and the coldest night fell to 6.4 °C, and the wettest single day dropped 46 mm — roughly 48% of the month's rain in one day.

September is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest September on record still delivered 191 mm against 42 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 96 mm average is a reasonable planning figure, not a promise.

Wind sits around 20.1 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 80%, high enough to notice on the warm days without dominating them.

How September sits in the year

The month is on the way down: 3.3 °C cooler than August, with October dropping another 5.9 °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 Sydney's extremes of 15.7 and 8.7 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 16.3 °C in September — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. This is the warmest the water gets all year.

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 Sydney versus nearby

If Sydney is one option among several, the nearby comparison is worth making. Halifax is close enough to be a coin toss — within a degree on temperature, 2 days less rain. Moncton 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 — 2 points behind July, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Sydney

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