Acadia National Park in January

June through October offers the best weather, but each month brings trade-offs. July and August deliver warm days (70-80°F) and the longest daylight hours, but also the biggest crowds and highest prices. Bar Harbor hotel rates can hit $400/night in peak summer. September is the sweet spot — comfortable temps, fewer crowds, and early fall colors starting to show. Plus, you'll still have warm enough weather for swimming at Sand Beach (though 'warm' is relative in Maine). October brings spectacular foliage but unpredictable weather. One day you're hiking in shorts, the next you need winter gear. November through May, the park transforms into a different world. Most services shut down, but you'll have trails largely to yourself. Winter hiking requires microspikes or snowshoes, and some trails close due to ice conditions. Here's the insider tip: late May and early June offer mild weather, blooming wildflowers, and reasonable lodging rates. The trade-off? Black fly season peaks in June — bring industrial-strength bug spray. For sunrise on Cadillac Mountain, you need to arrive by 4:30 AM in summer, but the parking lot fills fast. Consider staying overnight at Blackwoods Campground to beat the crowds.