Weather in Sydney in September

How September compares

September is the 8th warmest month of the year in Sydney and ranks 130th of 134 destinations we compare for September - see where else is hot in September. Against London's average high of 18.6°C in September, Sydney is 1.0°C warmer by day and 0.2°C warmer at night.

Daytime and night-time in September

The typical September day in Sydney peaks at 19.6°C, but that is an average: the warmest 10% of days reach 24.1°C or more. Roughly 1 in 14 days top 25°C and 1 in 143 pass 30°C. Nights average 11.4°C; one night in ten drops to 8.4°C or lower, so pack a layer for evenings - it is genuinely cool after dark. Between 1991 and 2020 the hottest September day here reached 33.0°C (2017-09-23) and the coldest night 4.9°C (2017-09-02).

Rain in September

Some rain (4-8 rainy days): about 6 days with 1 mm or more, 40 mm in total. Year to year it varies a lot - the wettest September was 1995 with 148 mm, the driest 2017 with 6 mm. Humidity averages 66%.

Sea temperature in September

The sea averages 17.7°C - too cold for most (under 18°c). Depending on the year it ranges from 16.7°C to 18.8°C. For the warmest sea here, come in February (23.0°C).

Sunshine and daylight

Around 7.4 hours of sunshine a day (estimated from cloud cover), 11.8 hours of daylight: the sun rises about 05:54 and sets about 17:47 local time in mid-September. Average cloud cover is 37%.

Is September a good time to visit Sydney?

September is not the strongest month here: mild days. The best months for Sydney on our scoring are December, January, February; months averaging 25°C or more: Jan, Feb.

Comfortable days, but keep a layer handy

The daytime average suits walking around without persistent heat, though September is not reliably warm enough to leave your jumper behind. The warmest 10% of days reach 24.1°C or more, so lighter clothing can get some use, especially around midday. At the other end, the coldest 10% of nights fall to 8.4°C or below. Pack clothes you can add and remove rather than dressing for summer throughout the trip. A jacket or warm jumper makes sense for evenings, particularly if you plan to sit outside. This month suits travellers who prefer mild conditions to heat, provided cool starts and evenings are not a disappointment.

Useful sunshine, with some room needed for rain

About 7.4 hours of sunshine within 11.8 hours of daylight gives September a useful balance for outdoor plans. That does not mean clear skies throughout the day, so avoid treating sunshine as guaranteed. There are about 6 rainy days, enough to justify a light waterproof and some flexibility rather than assuming every outing will stay dry. Keep weather-sensitive plans movable and check the forecast before committing to a long spell outdoors. The overall judgement is favourable for travellers happy to work around some rain: it need not define the trip, but packing only fair-weather clothing would be optimistic. Sun protection still belongs in your bag.

A cold sea changes the holiday calculation

The sea averages 17.7°C, which puts it in the cold category rather than comfortable holiday swimming territory. Its September range of 17°C to 19°C also means you should not plan around reliably warm water. Time beside the sea is a different proposition from spending much of the day in it; if you dislike cold water, swimming is best treated as optional. With a flight from London taking about 22 hours, that distinction matters. September makes more sense for a mild city holiday than a trip built around warmth. December, January and February rate better overall here if your timing is flexible.