Dunnville, Canada offers 2 beaches perfect for sunbathing, surfing, swimming, and more. Dunnville, Ontario, Canada, is known for its proximity to the Grand River and the annual Mudcat Festival. The best time to travel to Dunnville, Canada, is in July when the average air temperature is around 25°C (77°F) and the water temperature is approximately 22°C (72°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!