Though weather is just one factor, it can really affect your travel plans, especially if you are planning a longer stay in Istmina. The hottest months are usually March and February with an average temp of 77°F, while the coldest months are January and October with an average of 76°F. The rainiest months in Istmina are August, July, September, and June, with each month seeing an average of 69 inches of rainfall.