There’s nothing like an all-inclusive holiday in Port Moresby to refresh you, especially when you know what to expect from the elements. Here’s some information to help you choose when to book: The hottest months are usually December and November, with an average temperature of 27°C, while the coldest months are August and July, with an average of 25°C. July and August are the driest months, while March and January are the rainiest months.