Weather in Surabaya in January

Shoulder season. January sits in between. You will get good days and you will lose some. You should expect rain on 29 days of the month, which is more days wet than dry.

January ranks 6 of 12 in Surabaya: past the worst of the year but short of August, which is the month to book if the dates are open.

Rain on 29 of the month's 31 days, 13 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. Natural fibres and a second shirt for the day. At 85% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: 6 days top 30 °C — hot spells arrive, but they break; the day barely swings — 3.3 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest January day reached 33.9 °C and the coldest night fell to 24.2 °C, and the wettest single day dropped 68 mm — roughly 20% of the month's rain in one day.

January is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest January on record still delivered 510 mm against 161 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 337 mm average is a reasonable planning figure, not a promise.

Wind is light at 11.8 km/h, so the temperature on the page is close to the temperature on your skin, and humidity at 85% is the real story though — it is the number that decides how the day feels, not the 29 °C.

How January sits in the year

Temperatures hold steady either side: 29.7 °C in December, 29 here, 28.8 in February. Nothing about the timing within the month matters much.

Daylight in January

Surabaya sits close enough to the equator that daylight barely moves all year — 12.5 hours in January, against a range of just 0.8 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

Sea temperature

The sea sits at about 28.9 °C in January — warm enough that the water offers no relief from the heat. The sea peaks at 29.8 °C in April and bottoms out at 28.1 °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

Shoulder. The value months — prices ease off and you get the place closer to itself.

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

January in Surabaya versus nearby

If Surabaya is one option among several, the nearby comparison is worth making. Jepara is close enough to be a coin toss — within a degree on temperature, the same number of rain days. Semarang is close enough to be a coin toss — within a degree on temperature, 1 day less rain.

So: January is a compromise. August is 21 points better and is what Surabaya 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 Surabaya

See all twelve months in Surabaya, or where else to go in January.