The temperatures in the Mekong delta are all year round about 25-28°C with only slight variations.
The dry season in the Mekong delta from October / November to April / May is the preferred travel time. But even during the rainy season from May to October, the Mekong delta can be visited too. The rain usually comes in short, heavy showers, mostly in the afternoon and only lasts for an hour or so. Only a few days a year the temperature is below 20°C.
The main tourist season lasts from October to January. So far only a few tourists find their way into the Mekong delta during the off-season from March to September. Even though the weather at this time is not necessarily perfect, you have the advantage of more favorable prices and significantly fewer tourists.