Weather is probably a major factor when you plan your trip to Hai Duong, and keep 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 temp of 84°F, while the coldest months are January and December with an average of 67°F. The rainiest months in Hai Duong are August, September, July, and October, with each month seeing an average of 13 inches of rainfall.