Planning for the weather is an important factor for making your trip to Banjarmasin a success, especially when you're splurging. The hottest months are usually October and September with an average temp of 81°F, while the coldest months are July and August with an average of 80°F. The rainiest months in Banjarmasin are December, March, January, and November, with each month seeing an average of 13 inches of rainfall.