Acadia National Park sits at the intersection of coastal fog, Atlantic storms, and stunning fall foliage — making timing your visit more important than at most parks. Using Perfect Weather Index (PWI) scores calculated from daily National Weather Service forecast data, this page shows exactly when conditions are most comfortable on Mount Desert Island and when the coastal weather works against you.
Current Perfect Weather Index scores for the next 7 days at Acadia National Park. Higher scores indicate more comfortable outdoor conditions. Updated daily using National Weather Service forecast data.
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How to use this: Days with higher scores are generally better for hiking and outdoor activities, with more comfortable temperatures, lighter winds, and fewer weather impacts. → View official National Weather Service forecast for Acadia
September offers the most consistently comfortable weather at Acadia National Park, while August and July provide excellent hiking conditions during peak summer season.
Based on 2025 Perfect Weather Index (PWI) data from a coastal site near Acadia, the results reflect a classic coastal New England pattern: a cool, slow-building spring, a comfortable summer peak moderated by the Atlantic, and an exceptionally strong early fall season. Winter conditions are harsh and visitor access is significantly limited.
Raw monthly totals were normalized into monthly PWI scores (percent of possible points) and paired with the number of rare Perfect 10 days.
Monthly PWI scores reflect the percentage of possible comfort points earned at Acadia across all days in each month, based on 2025 National Weather Service forecast data. Perfect 10 days are days scoring a full 10 out of 10 on the PWI scale.
| Month | Monthly PWI Score | Perfect 10 Days | What It Means | Verdict |
|---|---|---|---|---|
| January | ~49% | 0 | Cold, windy, limited access | Avoid |
| February | ~50% | 0 | Deep winter conditions | Avoid |
| March | ~53% | 0 | Slow thaw, variable weather | Caution |
| April | ~58% | 0 | Cool, unsettled spring | Caution |
| May | ~67% | 1 | Improving, still brisk | Good |
| June | ~76% | 0 | Mild, reliable early summer | Very Good |
| July | ~76% | 0 | Warm but moderated by ocean | Very Good |
| August | ~80% | 0 | Most stable summer warmth | Excellent |
| September ⭐ | ~84% | 3 | Peak comfort, crisp air | Excellent |
| October | ~75% | 1 | Peak foliage, very reliable | Very Good |
| November | ~60% | 0 | Cold returns quickly | Caution |
| December | ~50% | 0 | Winter conditions dominate | Avoid |
PWI scores based on 2025 NWS forecast data at Furnace Creek. Scores at higher elevations within the park will differ.
Average monthly visitor counts at Acadia National Park (2019–2023 average, source: NPS). July and August are peak visitation months but September offers the highest PWI scores with significantly fewer visitors — making it the best value month for a comfortable, less crowded visit.
| Month | % of Annual Visitors | Avg Visitors | Crowd Level |
|---|---|---|---|
| January | <1% | 15,538 | Very Low |
| February | <1% | 14,071 | Very Low |
| March | 1% | 25,696 | Very Low |
| April | 2% | 95,165 | Low |
| May | 8% | 320,885 | Moderate |
| June | 15% | 599,015 | High |
| July | 20% | 791,025 | Peak |
| August | 20% | 795,332 | Peak |
| September | 16% | 646,116 | High |
| October | 14% | 567,466 | High |
| November | 2% | 76,388 | Low |
| December | <1% | 14,960 | Very Low |
Source: National Park Service visitor use statistics, 2019–2023 average.
September is the single best month to visit Acadia based on PWI data. Summer humidity has eased, temperatures are crisp and comfortable, Atlantic fog frequency drops significantly, and the park's trails are in peak condition. September also sees noticeably fewer visitors than July and August — making it the best combination of excellent weather and manageable crowds. Early fall foliage typically begins in late September, adding to the visual appeal.
August is Acadia's most stable summer month, with the highest summer PWI scores. Ocean temperatures moderate the heat that affects inland New England, and extended stretches of clear, comfortable weather are common. The tradeoff is crowd levels — July and August together account for 40% of annual visitors. If you visit in August, book accommodation and campsite reservations well in advance.
June and July both score 76% on the PWI scale — solid summer comfort with the Atlantic keeping temperatures moderate. Coastal fog is more common in June and early July than later in summer, which can reduce visibility on Cadillac Mountain but creates a dramatically atmospheric experience at sea level. Both months are excellent for hiking, kayaking, and cycling the carriage roads.
October scored 75% on the PWI scale in 2025, making it Acadia's second-best month for comfortable conditions. Fall foliage typically peaks in the first two weeks of October, drawing significant crowds despite cooling temperatures. The combination of colorful foliage, crisp air, and ocean views makes early October one of the most visually spectacular times to visit — but book well ahead as lodging fills quickly during peak foliage.
May is underrated for Acadia. Visitor numbers are a fraction of summer levels, the park is green and fresh after winter, and comfortable days are increasingly common by mid-month. Temperatures remain brisk — particularly in early May — but hikers and cyclists who don't mind cooler conditions will find the park far less crowded than summer months.
Winter at Acadia is cold, windy, and wet. PWI scores drop to the 49–60% range and many visitor facilities close or reduce hours. Snow is common from December through March. Several carriage roads and hiking trails may be icy or closed. The park remains accessible and genuinely beautiful in winter — particularly for experienced hikers and photographers — but it is not recommended for casual visitors expecting full park services.
Acadia's weather varies significantly across the park depending on elevation and proximity to the coast. The PWI scores on this page reflect conditions at sea level on Mount Desert Island — Cadillac Mountain summit conditions can be markedly different.
Coastal fog is a defining feature of Acadia's summer weather. It most commonly occurs in June and early July when warm, humid air moves over cold ocean water. Fog typically burns off by midday but can persist all day during certain weather patterns. The Schoodic Peninsula and higher elevations often have clearer conditions when the island is fogged in.
What is the best time to visit Acadia National Park?
September is the best month to visit Acadia based on Perfect Weather Index scores — peak comfort, crisp air, easing crowds, and early fall foliage. August is the best summer month, with the most stable warm conditions. If avoiding crowds is the priority, late May and early October offer respectable weather with significantly fewer visitors.
How cold does Acadia get in winter?
Winters at Acadia are cold and windy. January and February average highs in the low 30s°F (0°C) with lows regularly below 20°F (-7°C). Wind chill on Cadillac Mountain can make conditions feel significantly colder. PWI scores in winter drop to around 49–50%, reflecting genuinely uncomfortable outdoor conditions for casual visitors.
Does Acadia get fog?
Yes — coastal fog is a defining feature of Acadia's summer weather, particularly in June and early July. It typically forms when warm, humid air moves over cold ocean water and most commonly clears by midday. The Schoodic Peninsula on the mainland is often clearer than Mount Desert Island when fog is present. The Perfect Weather Index accounts for cloud cover and visibility in its scoring, so foggy days will score lower than clear days even if temperatures are comfortable.
When does fall foliage peak at Acadia?
Fall foliage at Acadia typically peaks in the first two weeks of October, though timing varies by year. The combination of coastal views, rocky shorelines, and colorful foliage makes early October one of the most visually spectacular times to visit. October also scores well on the PWI (75%), making it a genuinely comfortable month despite the cooler temperatures.
What is the best time to visit Acadia for European visitors?
September is ideal for European visitors — peak weather comfort, fewer crowds than summer, and early fall foliage beginning. July and August are also excellent if summer travel is preferred. Acadia is easily combined with Boston (approximately 5 hours by car) and other New England destinations. Many European visitors fly into Boston and drive up the coast through Portland, Maine on the way to Bar Harbor.
What is the Perfect Weather Index?
The Perfect Weather Index (PWI) is a daily comfort score from 1–10 calculated from National Weather Service forecast data. It combines temperature, sunshine, humidity, wind, and precipitation into a single rating. A score of 8 or higher means genuinely excellent outdoor conditions. Scores below 4 reflect cold, storms, or other conditions that significantly limit outdoor comfort. Learn more about how the PWI works →