Weather in Sendai in September

A good month. September is a solid month to be in Sendai. You should expect rain on 16 days of the month, which is more days wet than dry.

September ranks 3 of 12 in Sendai. Only May scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain on 16 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: 4 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest September day reached 35.1 °C and the coldest night fell to 4.7 °C, and the wettest single day dropped 117 mm — roughly 82% of the month's rain in one day.

September is moderately variable: 42 mm in the driest year against 282 mm in the wettest, around an average of 142 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 2.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity at 87% is the real story though — it is the number that decides how the day feels, not the 25.4 °C.

How September sits in the year

The month is on the way down: 4.5 °C cooler than August, with October dropping another 6.5 °C. The first week and the last are not the same trip.

Daylight in September

12.5 hours of daylight, losing 1.2 hours across the month. That is between Sendai's extremes of 14.8 and 9.5 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 23 °C in September — comfortable for a proper swim. This is the warmest the water gets all year.

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.

September in Sendai versus nearby

If Sendai is one option among several, the nearby comparison is worth making. Niigata is close enough to be a coin toss — within a degree on temperature, 1 day less rain. Utsunomiya is close enough to be a coin toss — within a degree on temperature, 1 day less rain.

So: September works, with May the better month by 8 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Sendai

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