Weather will likely play an important role when you plan your trip to La Merced, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually September and October with an average temp of 70°F, while the coldest months are July and August with an average of 68°F. The rainiest months in La Merced are February, January, December, and March, with each month seeing an average of 13 inches of rainfall.