Weather in Greymouth in September

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

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

Rain on 18 days, 6 of them heavy. Enough to need a plan B, not enough to need a plan around it. Layers, and a genuinely waterproof outer — at 13.3 °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 — 5.2 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 18 °C and the coldest night fell to 1.9 °C, and the wettest single day dropped 43 mm — roughly 27% of the month's rain in one day.

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 282 mm against 78 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 158 mm average is a reasonable planning figure, not a promise.

Wind is light at 4.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 85%, which at 13.3 °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: 12 °C in August, 13.3 here, 14.4 in October. Nothing about the timing within the month matters much.

Daylight in September

11.7 hours of daylight, gaining 1.4 hours across the month. That is between Greymouth's extremes of 15.3 and 9.1 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 13.3 °C in September — too cold to swim without a wetsuit. The sea peaks at 18.5 °C in February and bottoms out at 13.3 °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

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

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

September in Greymouth versus nearby

If Greymouth is one option among several, the nearby comparison is worth making. Waikowhai is close enough to be a coin toss — within a degree on temperature, the same number of rain days. Christchurch is a better bet in September — within a degree on temperature, 5 days less rain.

So: September is a compromise. February is 28 points better and is what Greymouth 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 Greymouth

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