Weather in Invercargill in September

A hard month. September is a hard month in Invercargill, and worth planning around. You should expect rain on 18 days of the month, which is more days wet than dry.

September ranks 7 of 12 in Invercargill: past the worst of the year but short of February, which is the month to book if the dates are open.

This is persistent light rain rather than storms: 18 wet days but only 2 heavy ones. It rarely cancels anything outright, and it rarely fully clears either. A jacket beats an umbrella. Layers, and a genuinely waterproof outer — at 11.8 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

Averages flatten a month, and this one hides a few things: the day barely swings — 4.6 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 18.2 °C and the coldest night fell to 2.5 °C.

September is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest September on record still delivered 181 mm against 48 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 103 mm average is a reasonable planning figure, not a promise.

Wind sits around 16.3 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 81%, which at 11.8 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How September sits in the year

Temperatures hold steady either side: 10.4 °C in August, 11.8 here, 12.8 in October. Nothing about the timing within the month matters much.

Daylight in September

11.7 hours of daylight, gaining 1.6 hours across the month. That is between Invercargill's extremes of 15.8 and 8.6 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 10 °C in September — too cold to swim without a wetsuit. The sea peaks at 12.7 °C in February and bottoms out at 9.9 °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

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

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

September in Invercargill versus nearby

If Invercargill is one option among several, the nearby comparison is worth making. Papatowai is close enough to be a coin toss — within a degree on temperature, 3 days less rain. Te Anau is close enough to be a coin toss — within a degree on temperature, 3 days more rain.

So: September is a compromise. February is 21 points better and is what Invercargill is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Invercargill

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