The highest day temperature in September 2025 was 99°F. The lowest night temperature was 80°F. The average values for day and night temperatures during September were 95.1°F и 82.0°F respectivly.

The average sea surface temperature in September 2025 for Surabaya was 88.6°F. The maximum and minimum values were 87.2°F and 90.8°F respectively.

Most of the days in September are sunny but you can also expect cloudy and gloomy days.

Precipitation total in September for Surabaya is 0.6 in. It makes september one of the least rainy months of the year.

The average wind speed in September is 6.7 mph. This value is relatively stable throughout the year.

We are using day length and cloud cover information for each day of the month to calculate averages for this chart. Average sunny hours for Surabaya in September is 10.3 hours.