Onekama, United States offers 2 beaches perfect for sunbathing, surfing, swimming, and more. Onekama, Michigan, United States, is known for Portage Lake and its access to Lake Michigan, as well as the scenic M-22 highway. The best time to travel to Onekama, United States, is in July when the average air temperature is around 70°F (21°C) and the water temperature is approximately 68°F (20°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!