Weather in Cairns in September

Prime time. September is about as good as Cairns gets. Highs average 29 °C, lows 20.2 °C, and rain falls on 6 days — nothing in the month is working against you.

September ranks 4 of 12 in Cairns: past the worst of the year but short of August, which is the month to book if the dates are open.

Rain falls on only 6 days, so an itinerary with no wet-weather fallback is a reasonable risk. Pack for 29 °C days and 20.2 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: 9 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest September day reached 35.9 °C and the coldest night fell to 13.8 °C, and the wettest single day dropped 32 mm — roughly 103% of the month's rain in one day.

This is the volatile part. September rainfall has ranged from 2 mm to 122 mm across the twenty years measured — a 120 mm spread around an average of 31 mm. The average is real but almost no individual September looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 6.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 74%.

How September sits in the year

The month is on the way up: 2.4 °C warmer than August, and October adds another 2.1 °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

12 hours of daylight, gaining 0.5 hours across the month. That is between Cairns's extremes of 13.1 and 11.1 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 25.2 °C in September — warm enough to stay in as long as you like. The sea peaks at 29.2 °C in February and bottoms out at 24.7 °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

Busy. Popular without being frantic; book the things you care about, improvise the rest.

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

September in Cairns versus nearby

If Cairns is one option among several, the nearby comparison is worth making. Port Douglas is a better bet in September — 2 °C cooler, the same number of rain days. Townsville is close enough to be a coin toss — within a degree on temperature, 4 days less rain.

So: September works, with August the better month by 10 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Cairns

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