Weather in Thanh Hóa in September

A hard month. September is a hard month in Thanh Hóa, and worth planning around. You should expect rain on 20 days of the month, which is more days wet than dry.

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

Rain on 20 of the month's 30 days, 9 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: 20 days top 30 °C, making the heat continuous rather than occasional; the day barely swings — 6 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 35.2 °C and the coldest night fell to 19.4 °C, and the wettest single day dropped 148 mm — roughly 48% 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 540 mm against 154 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 309 mm average is a reasonable planning figure, not a promise.

Wind is light at 6.9 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 30.6 °C.

How September sits in the year

Temperatures hold steady either side: 31.6 °C in August, 30.6 here, 28.3 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 5 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 Thanh Hóa's extremes of 13.3 and 10.9 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 29.5 °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 Thanh Hóa versus nearby

If Thanh Hóa is one option among several, the nearby comparison is worth making. Vinh is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Hanoi is close enough to be a coin toss — within a degree on temperature, 2 days less rain.

So: September is a compromise. February is 48 points better and is what Thanh Hóa 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 Thanh Hóa

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