Planning for the weather is a good way to make your trip to Hai Phong relaxing and enjoyable, especially when you’re splurging. 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 66°F. The rainiest months in Hai Phong are August, September, July, and October, with each month seeing an average of 13 inches of rainfall.