Thunder Hole is accessible in winter, however the park will close the road during snow storms and then clean it up and reopen Ocean Drive after the storm is over. To get there in the winter you drive down Schooner Head Road and turn right at the 4 way stop at the end. Turn left onto the one way park loop road and go through the entrance station. Stop at Sand Beach for a bit, and then continue to Thunder Hole. The road closes just before Otter Cliffs, so you’ll be forced to turn right onto Otter Cliff Road instead of continuing on Park Loop Road. At the end of Otter Cliff Road turn right to head back to Bar Harbor.

A recent change is they now man the entrance station some of the time in winter, and you’re supposed to display a pass regardless, so you’ll want a park pass. You can buy one at the entrance station, at the chamber of commerce on Bar Harbor (the park shares it in the winter because the ANP visitors center is closed), or online. In the winter sometimes they sell discounted annual passes (in person only). They used to advertise that passes were only required May-October, but that is no longer the case.

A large portion of the Park Loop Road is closed to cars in winter, but it’s currently snow free and great for biking.