O'Brien, United States offers 2 beaches perfect for sunbathing, surfing, swimming, and more. O'Brien, Florida, United States, is known for its proximity to the Ichetucknee Springs State Park. The best time to travel to O'Brien, United States, is during the summer months of June to August, when the average air temperature is around 75°F (24°C) and the water temperature in nearby lakes and rivers 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!