Weather in Sydney in September

Prime time. If you get to pick your dates, September is the one. Highs average 19.5 °C, lows 13.5 °C, and rain falls on 7 days — nothing in the month is working against you.

Sydney barely has seasons. September scores 86 out of 100 against a best of 86 in September — a gap small enough that the month you choose matters far less here than the week you choose.

Rain on 7 days, 1 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; the day barely swings — 6 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 28.5 °C and the coldest night fell to 9.2 °C, and the wettest single day dropped 43 mm — roughly 100% of the month's rain in one day.

September is moderately variable: 1 mm in the driest year against 118 mm in the wettest, around an average of 43 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 11.4 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 68%.

How September sits in the year

The month is on the way up: 2.3 °C warmer than August, and October adds another 2 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short.

Daylight in September

11.8 hours of daylight, gaining 1 hours across the month. That is between Sydney's extremes of 14.4 and 9.9 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 18.8 °C in September — swimmable, but it takes a moment to commit. The sea peaks at 24.1 °C in February and bottoms out at 18.7 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead. If the dates are flexible, April is the trade worth considering — 5 points weaker on weather, and materially quieter.

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. Central Coast is close enough to be a coin toss — 2.1 °C warmer, 1 day less rain. Katoomba is the weaker option in September — 3.6 °C cooler, 1 day less rain.

So: September is the answer for Sydney. If it is booked out or priced out, October is the next best thing at 3 points behind, and June is the month to keep off the shortlist.

Every month in Sydney

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