Weather in Perth in December

Prime time. If you get to pick your dates, December is the one. Highs average 24.6 °C, lows 17.9 °C, and rain falls on 3 days — nothing in the month is working against you.

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

Rain falls on only 3 days, so an itinerary with no wet-weather fallback is a reasonable risk. 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: 4 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest December day reached 36.2 °C and the coldest night fell to 12.8 °C.

This is the volatile part. December rainfall has ranged from 0 mm to 39 mm across the twenty years measured — a 39 mm spread around an average of 12 mm. The average is real but almost no individual December looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind sits around 20 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity is unremarkable at 65%.

How December sits in the year

The month is on the way up: 2.2 °C warmer than November, and January adds another 1.8 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short.

Daylight in December

December is at or near the longest days of Perth's year: 14.2 hours of daylight, holding steady all month. Evenings are the real gain — dinner outdoors still happens in full light.

Sea temperature

The sea sits at about 20.8 °C in December — swimmable, but it takes a moment to commit. The sea peaks at 22.9 °C in March and bottoms out at 19 °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.

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

December in Perth versus nearby

If Perth is one option among several, the nearby comparison is worth making. Bunbury is close enough to be a coin toss — 3.8 °C warmer, the same number of rain days. Geraldton is close enough to be a coin toss — within a degree on temperature, 1 day less rain.

So: December is effectively as good as it gets here — 2 points behind January, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Perth

See all twelve months in Perth, or where else to go in December.