Weather is probably a major factor when you plan your trip to Hai Duong, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually June and July, with an average temperature of 29°C, while the coldest months are January and December, with an average of 19°C. The rainiest months in Hai Duong are August, September, July and October, with each month seeing an average of 337 mm of rainfall.