Weather in Mount Gambier in December

Prime time. December is about as good as Mount Gambier gets. Highs average 20 °C, lows 12.6 °C, and rain falls on 8 days — nothing in the month is working against you.

December ranks 4 of 12 in Mount Gambier: past the worst of the year but short of January, which is the month to book if the dates are open.

Rain on 8 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

The averages here are honest — no hidden extremes worth planning around. Across the twenty years measured, the hottest December day reached 36.9 °C and the coldest night fell to 8.6 °C, and the wettest single day dropped 62 mm — roughly 144% of the month's rain in one day.

December is moderately variable: 12 mm in the driest year against 113 mm in the wettest, around an average of 43 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind is light at 13.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 71%.

How December sits in the year

The month is on the way up: 1.6 °C warmer than November, and January 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 December

December is at or near the longest days of Mount Gambier's year: 14.8 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 15.9 °C in December — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. The sea peaks at 17.9 °C in February and bottoms out at 13.7 °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.

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

December in Mount Gambier versus nearby

If Mount Gambier is one option among several, the nearby comparison is worth making. Warrnambool is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Ballarat is close enough to be a coin toss — 5 °C warmer, 1 day less rain.

So: December is effectively as good as it gets here — 5 points behind January, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Mount Gambier

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