Weather in Wellington in September

Shoulder season. September sits in between. You will get good days and you will lose some. Highs sit at 13 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

September ranks 9 of 12 in Wellington: past the worst of the year but short of February, which is the month to book if the dates are open.

Rain on 11 days, 2 of them heavy. Enough to need a plan B, not enough to need a plan around it. Layers, and a genuinely waterproof outer — at 13 °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 — 3.4 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 16.7 °C and the coldest night fell to 6 °C, and the wettest single day dropped 36 mm — roughly 51% of the month's rain in one day.

September is moderately variable: 8 mm in the driest year against 143 mm in the wettest, around an average of 70 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind sits around 21.3 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 83%, which at 13 °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: 11.9 °C in August, 13 here, 14.1 in October. Nothing about the timing within the month matters much.

Daylight in September

11.8 hours of daylight, gaining 1.3 hours across the month. That is between Wellington's extremes of 15.1 and 9.2 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 11.7 °C in September — too cold to swim without a wetsuit. The sea peaks at 16.8 °C in February and bottoms out at 11.6 °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 Wellington versus nearby

If Wellington is one option among several, the nearby comparison is worth making. Nelson is close enough to be a coin toss — 2.2 °C warmer, 3 days more rain. Palmerston North is close enough to be a coin toss — within a degree on temperature, 3 days more rain.

So: September is a compromise. February is 27 points better and is what Wellington 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 Wellington

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