The best time to visit Monhegan Island for pleasant weather and full access to amenities is from late May to early October.These months offer the warmest temperatures and the most sunshine, making outdoor activities like hiking and exploring the island's natural beauty most enjoyable. All local businesses, including restaurants, shops, and art galleries, are typically open during this period, ensuring a complete visitor experience.For travelers who appreciate cooler weather and fewer crowds, especially those interested in photography or birdwatching, early June and late September are ideal.