Weather will likely play an important role when you plan your trip to Island Park, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually July and August, with an average temperature of 15°C, while the coldest months are December and January, with an average of -8°C. The snowiest months in Island Park are February, March, January and October, with each month seeing an average of 41 cm of snowfall.