Weather in Jakarta in September

Shoulder season. September is shoulder season in Jakarta — cheaper, quieter, and a genuine gamble. Highs average 30.5 °C, lows 24.9 °C, and rain falls on 12 days — nothing in the month is working against you.

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

Rain on 12 days, 2 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 30.5 °C days and 24.9 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: 22 days top 30 °C, making the heat continuous rather than occasional; the day barely swings — 5.5 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 33.1 °C and the coldest night fell to 22.2 °C, and the wettest single day dropped 25 mm — roughly 38% of the month's rain in one day.

This is the volatile part. September rainfall has ranged from 3 mm to 268 mm across the twenty years measured — a 265 mm spread around an average of 66 mm. The average is real but almost no individual September looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 8.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 76%, high enough to notice on the warm days without dominating them.

How September sits in the year

Temperatures hold steady either side: 29.6 °C in August, 30.5 here, 30.8 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 8 days more of it, so the earlier half of a flexible trip is the safer half.

Daylight in September

Jakarta sits close enough to the equator that daylight barely moves all year — 12.1 hours in September, against a range of just 0.7 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 September — warm enough that the water offers no relief from the heat. The sea peaks at 29.9 °C in May and bottoms out at 28.6 °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. September is the value pick for Jakarta: it scores within 9 points of August without carrying August's prices.

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

September in Jakarta versus nearby

If Jakarta is one option among several, the nearby comparison is worth making. Bandung is close enough to be a coin toss — 2.4 °C cooler, the same number of rain days. Bandar Lampung is close enough to be a coin toss — within a degree on temperature, 3 days less rain.

So: September works, with August the better month by 9 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Jakarta

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