Planning for the weather is a good way to make your trip to Koumac relaxing and enjoyable, especially when you're splurging. The hottest months are usually February and January, with an average temperature of 26°C, while the coldest months are August and July, with an average of 22°C. The rainiest months in Koumac are March, January, February and April, with each month seeing an average of 188 mm of rainfall.