Weather in Haiphong in September

A hard month. September asks something of you. Go in knowing what. You should expect rain on 19 days of the month, which is more days wet than dry.

September ranks 8 of 12 in Haiphong: past the worst of the year but short of December, which is the month to book if the dates are open.

This is wet-season rain: 19 wet days and 8 genuinely heavy ones, which in this climate means concentrated downpours rather than all-day grey. The pattern is usually a clear morning and a loud afternoon, so front-load the day and stop fighting the 3pm hour. Natural fibres and a second shirt for the day. At 83% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: 20 days top 30 °C, making the heat continuous rather than occasional; the day barely swings — 5.4 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 35.3 °C and the coldest night fell to 19.3 °C, and the wettest single day dropped 103 mm — roughly 43% of the month's rain in one day.

September is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest September on record still delivered 377 mm against 101 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 240 mm average is a reasonable planning figure, not a promise.

Wind is light at 7.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 83%, high enough to notice on the warm days without dominating them.

How September sits in the year

Temperatures hold steady either side: 31 °C in August, 30.6 here, 28.6 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 8 days less of it, so pushing the dates later buys drier weather.

Daylight in September

12.3 hours of daylight, losing 0.6 hours across the month. That is between Haiphong's extremes of 13.4 and 10.9 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 29.4 °C in September — warm enough that the water offers no relief from the heat. This is the warmest the water gets all year.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

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

September in Haiphong versus nearby

If Haiphong is one option among several, the nearby comparison is worth making. Hanoi is close enough to be a coin toss — within a degree on temperature, 1 day less rain. Thanh Hóa is close enough to be a coin toss — within a degree on temperature, 1 day more rain.

So: September is a compromise. December is 45 points better and is what Haiphong 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 Haiphong

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