Weather in Niigata in December

The month to avoid. Of the twelve, December is the one to avoid. You should expect rain on 25 days of the month, which is more days wet than dry.

December ranks 9 of 12 in Niigata: past the worst of the year but short of June, which is the month to book if the dates are open.

Rain on 25 of the month's 31 days, 8 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Layers, and a genuinely waterproof outer — at 9.3 °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 — 2.9 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 17.7 °C and the coldest night fell to -0.8 °C, and the wettest single day dropped 54 mm — roughly 25% of the month's rain in one day.

December is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest December on record still delivered 400 mm against 113 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 215 mm average is a reasonable planning figure, not a promise.

Wind sits around 21.4 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 79%, which at 9.3 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How December sits in the year

The month is on the way down: 5.1 °C cooler than November, with January dropping another 3 °C. The first week and the last are not the same trip. Rain has already shifted: 5 days more than November had.

Daylight in December

December sits at the dark end of Niigata's year — 9.6 hours of daylight against 14.8 at midsummer, holding steady all month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

Sea temperature

The sea sits at about 14.6 °C in December — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. The sea peaks at 26.2 °C in August and bottoms out at 9.8 °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.

December in Niigata versus nearby

If Niigata is one option among several, the nearby comparison is worth making. Sendai is the weaker option in December — 4.2 °C cooler, 2 days less rain. Utsunomiya is a better bet in December — within a degree on temperature, 19 days less rain.

So: December is a compromise. June is 46 points better and is what Niigata 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 Niigata

See all twelve months in Niigata, or where else to go in December.