The best time to visit New Castle, New Hampshire is during the summer months, from June to August, when the weather is warm and ideal for enjoying the coastal activities.During this period, temperatures are generally pleasant, ranging from the mid-60s to high 70s Fahrenheit, making it comfortable for exploring the island and its surroundings. The ocean is also warm enough for swimming and various water sports. Many local businesses, restaurants, and attractions are fully operational with extended hours, offering the complete New Castle experience.Couples looking for a romantic getaway will appreciate the picturesque coastal scenery and opportunities for leisurely strolls along the shore or enjoying sunset views. The warm evenings are great for dining al fresco at one of the island's fine restaurants.Families also find summer an excellent time to visit. The calm waters provide a nice setting for children to play, and there are often family-friendly events and activities taking place in the nearby Portsmouth area.