Weather in Sapporo in September

A good month. September works. It is not the peak, but nothing about it fights you. You should expect rain on 15 days of the month, which is more days wet than dry.

September ranks 4 of 12 in Sapporo: past the worst of the year but short of June, which is the month to book if the dates are open.

Rain on 15 days, 4 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

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average September reaches 30 °C. Across the twenty years measured, the hottest September day reached 31.4 °C and the coldest night fell to 5.7 °C, and the wettest single day dropped 100 mm — roughly 73% 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 286 mm against 52 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 137 mm average is a reasonable planning figure, not a promise.

Wind is light at 4.2 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 85%, high enough to notice on the warm days without dominating them.

How September sits in the year

The month is on the way down: 4 °C cooler than August, with October dropping another 6.8 °C. The first week and the last are not the same trip.

Daylight in September

12.6 hours of daylight, losing 1.4 hours across the month. That is between Sapporo's extremes of 15.3 and 9 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 20.4 °C in September — swimmable, but it takes a moment to commit. This is the warmest the water gets all year.

How busy it gets

Busy. Popular without being frantic; book the things you care about, improvise the rest.

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

September in Sapporo versus nearby

If Sapporo is one option among several, the nearby comparison is worth making. Sendai is close enough to be a coin toss — 3.5 °C warmer, 1 day more rain. Niigata is close enough to be a coin toss — 2.8 °C warmer, the same number of rain days.

So: September works, with June the better month by 11 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Sapporo

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