Diamond Harbour, New Zealand offers 1 beach perfect for sunbathing, surfing, swimming, and more. Diamond Harbour, Canterbury, New Zealand, is known for its stunning views of Lyttelton Harbour and the Port Hills. The best time to visit Diamond Harbour, New Zealand, is during the summer months of December to February, when the average air temperature is around 20°C (68°F) and the water temperature is approximately 17°C (63°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!