Thunder Hole

People gather on stairs leading down a cliff from a road to the ocean

At high tide or during storms, Thunder Hole transforms into a roaring spectacle as waves compress into a narrow granite chasm and expel trapped air with thunderous force. The inlet was carved over millennia by wave and tidal erosion into the eastern granite shoreline of Mount Desert Island. Descend the stairs at low tide to examine the smoothed cliff walls and cavitation pits—evidence of sustained wave abrasion. Visit 1–2 hours before high tide for the best acoustic and visual experience.

Access & viewing

GPS Coordinates: 44.3210037005,-68.1890475002
Accessibility: Paved parking lot with wheelchair-accessible reserved spaces. Upper viewing area accessible via paved walkway. Optional stairs and accessible ramp with switchbacks for descent to lower cliff viewing area (reconstructed 1992–1993).

Conditions & safety

Permits Required: 0

Planning advice

Nearby Attractions: Ocean Path Trail, Otter Point (adjacent on Park Loop Road), Sand Beach, Jordan Pond
Nearby Facilities: Thunder Hole Gift Shop (snacks, souvenirs, housed in historic 1934 ranger station); restrooms; accessible parking
Best Time To Visit: Visit 1–2 hours before high tide with incoming swells. Wave height matters more than tidal height—storm surge and Atlantic swells increase the phenomenon's intensity.
Tips Advice: Listen for subsonic rumble as compressed air exits the chasm—it's wave energy converting to sound in real time.
At low tide, examine granite for smooth scours from wave abrasion and deeper pits where cavitation occurred.
Wave spray contains sand and fine debris—observe air-abrasion polishing patterns on exposed rock faces.
Bring a rain jacket if windy; spray is saltwater and cold.
Never put hands near surge channels or unrailed ledges. Water temperature stays 40–50°F year-round.
Insider Tips: Timing is everything: high tide with incoming swell = roaring phenomenon; low tide = quiet but reveals erosion patterns.
The granite cliff walls are smoothed and polished from abrasion—run your hand along them to feel the wave-worn surface.
Passé stamp collectors: this is an official NPS passport location.
Summer weekday mornings (before 9am) offer fewer crowds and reliable weather for photography.

More details

Park Area: Eastern shore, Park Loop Road
Family Friendly Notes: Accessible for families with children, but requires supervision due to cliff edges and rogue wave risk. Railings and reconstructed walkways in place. Rule: never turn your back to the ocean, keep children at arm's length near water.
Recent Updates: Accessible ramp with switchbacks reconstructed 1992–1993; walkway systems upgraded in 1960s; restrooms constructed in 1982; gift shop operates in historic 1934 WPA-era ranger station
Attraction Type: Geological Formation
Elevation Feet: 0
Accessibility Level: Drive-up view with optional stairs to lower cliffs
How To Get There: Located on Park Loop Road (paved, eastern section) on the rocky eastern shoreline of Mount Desert Island. Park in the small lot with wheelchair-accessible reserved spaces. Alternatively, walk Ocean Path trail to reach it. Island Explorer shuttle (free, summer only) stops here.
Parking Availability: Small parking lot; fills by 8–10am during peak summer season (June–August); wheelchair-accessible reserved spaces available
Road Type: Paved (Park Loop Road)
Seasonal Access: Park Loop Road typically open mid-April through early December (weather dependent)
Entry Fees: $35 per vehicle (7-day pass); $20 per person (7-day pass); $30 motorcycle (7-day pass); youth 15 and under free
Main Features: Granite inlet with narrow channel; wave compression and air expulsion phenomenon; 40+ foot wave spray potential; carved granite cliff faces with striations and cavitation pits; tidal variation effects; accessible viewing stairs at lower cliff level.
What Youll See: Granite inlet with narrow channel; wave compression spray; smooth cliff faces scoured by wave abrasion; cavitation pits and striations; Atlantic swells and surge; tidal variation effects
Unique Characteristics: National Park Service passport stamp location; wave-carved granite inlet listed on National Register of Historic Places; houses historic 1934 WPA-era ranger station (now gift shop)
Safety Considerations: Rogue waves can wash over surrounding granite ledges without warning, even in calm weather—never turn your back to the ocean. Cliff edge exposure is significant; stay behind railings. Wave spray reaches 40+ feet and water is 40–50°F year-round. In storms, sections of walkway close. Supervise children carefully.
Best Viewpoints: Upper parking area for wide-angle wave spray observation; stairs midpoint for wave height perspective; lower cliff viewing for close-up erosion detail and texture
Photo Opportunities: Wave spray silhouetted against sky at high tide; sunrise light on cliff striations; wave impact spray with mist backlit; sunset over Atlantic swells
Sunrise Sunset Quality: Sunrise: strong eastward light on cliff faces and spray creates golden illumination; sunset: backlighting over Atlantic swells creates silhouette drama
Visitor Center Present: 0
Restrooms Available: 1
Picnic Areas: 0
Interpretive Signs: 1
Water Available: 0
Guided Tours Available: 0
Trailheads Here: Ocean Path Trail
Connecting Trails: Ocean Path Trail
Nearby Services: Hulls Cove Visitor Center (southwest via Park Loop Road); food, lodging, and supplies in Bar Harbor town
Geological Formation Type: Wave-carved granite inlet (coastal erosional feature)
Scientific Interest: Coastal wave erosion mechanics; granite abrasion patterns and cavitation evidence; tidal phenomenon with compressed air expulsion; subsonic wave energy conversion
Road Opening Dates: Mid-April (typical); Park Loop Road typically opens mid-April
Best Visit Times: Early morning (before 9am) or after 3pm during summer; shoulder season mornings for solitude
Best Season: Summer (June–August) for reliable access and stable weather; shoulder seasons (May, September–October) for fewer crowds and larger Atlantic swells
Weather Patterns: Atlantic coastal weather with frequent fog in early summer; afternoon thunderstorms July–August; larger swells September–October and winter storms increase wave height and phenomenon intensity
Peak Fill Times: Parking lot fills by 8–10am during peak summer season
Busiest Season: Summer (June–August), especially July–August when Island Explorer shuttle operates
Fishing Nearby: 0
Swimming Allowed: 0
Boating Allowed: 0
Climbing Areas: 0
Review Summary: Visitors consistently appreciate the unique acoustic and visual phenomenon; many understand the wave erosion mechanics after visiting. Disappointment occurs if tides or swells don't align, emphasizing the importance of timing. Most rate it a must-see on Acadia itineraries for the roaring effect and dramatic granite coastal landscape.
Sources: National Park Service — Thunder Hole (official page): https://www.nps.gov/places/thunder-hole.htm: 2026-07-15
National Park Service — Acadia National Park fees, hours & conditions: https://www.nps.gov/acad/index.htm: 2026-07-05
Climate data: McFarland Hill, Acadia NP, 470 ft (NOAA 1991-2020 normals, station USC00170100)

Location

Frequently asked questions

Is the roaring sound really that loud?

Yes. Compressed air exits the chasm with explosive force, creating subsonic rumble audible from the upper parking lot. During large swells, it's genuinely deafening. The sound is pure wave-driven physics.

Do I need special fitness or skills?

No. Upper viewing area is car-accessible with paved walkway. Optional stairs lead to lower cliff faces but aren't required. Railings and reconstructed walkways are maintained and safe.

What's the best time to visit?

Visit 1–2 hours before high tide with incoming swells or storm surge. At low tide, it's quiet but you can inspect erosion patterns and striations close-up on the cliff walls.

Is this safe for kids?

Yes, with supervision. Railings, stairs, and paved pathways are in place. Rule: never turn your back to the ocean, keep children at arm's length near ledges. Water temperature is 40–50°F year-round.

Can rogue waves wash over me?

Yes—rogue waves can wash over ledges without warning, even in calm weather. This is why railings and maintained walkways exist. The stairs and lower viewing area keep you at safe vantage points. Bring a rain jacket if windy.