Planning for the weather is an important factor for making your trip to Cát Bà a success, especially when you're splurging. The hottest months are usually July and June, with an average temperature of 28°C, while the coldest months are January and December, with an average of 19°C. The rainiest months in Cát Bà are August, July, September and June, with each month seeing an average of 386 mm of rainfall.