Hyannis (Cape Cod) weather in August
August in Hyannis: hot, a little rain, with muggy air — one of the best months to visit.
Updated September 2026 · climate normals from ERA5 reanalysis
#2 of 12 months in Hyannis · #328 of 1413 destinations to visit in August · comfort 88/100 (tier A)
- Days
- 27°C
- Nights
- 18°C
- Wet days
- 7
- Sun
- 10.8 h
- Humidity
- 81%
- Daylight
- 14 h
Traveller notes on Hyannis in August
Forum posters describe August as typically the warmest month, often in the 80s-90sF and humid, though the Cape's ocean breezes keep it noticeably cooler than inland Massachusetts at the same time - a stretch of 90F+ days is possible, but so is a cooler, rawer spell within the same month. Posters call August rain genuinely unpredictable, ranging from a light sprinkle to a full washed-out day, though it's typically the lowest-rain month of the summer overall. Mosquitoes are a real, near-constant presence, especially in the evenings, with repellent treated as standard packing. Posters consistently name the last two weeks of August through September as the more reliably pleasant stretch compared to June or early August.
Other months in Hyannis
Cape Cod's own forum doesn't sugarcoat February: expect a real chance of high wind, biting cold and snow, and New England weather here is notoriously hard to predict from one day to the next. Multiple posters recommended layering with fleece under a windproof shell so you can still get outside comfortably. A good number of shops and restaurants that cater to the summer crowd simply close for the season, so plan meals ahead rather than expecting to wander and find something open. It's a legitimate visit for solitude and off-season prices, just not the postcard version of the Cape.
Add your own note from Hyannis's card on the map.
Hyannis climate normals — August
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Hyannis in August
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
Peak crowdsIsland ferry high season, Peak summer season, Summer break in United States(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Hyannis's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Best weatherHyannis's weather peaks June–August, best around July.
August includes White shark season.
Best weatherFair weatherToughest weather
What's on in Hyannis in August
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Opening
Island ferry high season
20 May – 15 Oct · usuallySummer season opensCrowdedBook earlyHyannis is the mainland end of the Nantucket boats, and the summer timetable adds fast ferries and extra sailings from late May. Car spaces on the traditional boat are released months ahead and go the day they open. Source ↗
- Nature
White shark season
1 Jun – 31 Oct · usuallyWildlife seasonRiskWhite sharks follow the grey seals into Cape waters from early summer and are gone by late autumn, with the tagged detections peaking in August and September. It is the ocean side that closes for sightings, not the calmer Nantucket Sound beaches in town. Source ↗
- Season
Peak summer season
1 Jul – 31 AugSchool holidaysCrowdedBook earlyThe whole Cape funnels through here for the boats, and Route 6 and the rotaries jam every Friday afternoon and Sunday evening. Main Street is at its best on a weekday morning before the day-boats land.
- Hazard
Hurricane season
15 Aug – 31 Oct · usuallyClosuresNew England catches the tail of Atlantic systems in late summer and autumn, and even a passing storm cancels the island ferries and takes the power out for a day or two. Direct hits are rare; disrupted travel is not. Source ↗
Nearby, and something's on
Within 300 km of Hyannis — a day trip or a short hop — with something on this month. Never part of the comfort score.
Where is Hyannis?
Hyannis in August — FAQ
- Is August a good time to visit Hyannis?
- August in Hyannis: hot, a little rain, with muggy air — one of the best months to visit. It ranks #2 of 12 months for Hyannis on SeasonMap's comfort score (88/100).
- What is the weather like in Hyannis in August?
- In August, Hyannis averages a daily high of 26.8°C and a low of 18.1°C, with about 78.6 mm of rain over roughly 6.9 rainy days.
- What is the air quality in Hyannis in August?
- Hyannis has a mean US Air Quality Index of about 58 in August.
Within 300 km: Newport's Newport Jazz Festival on 31 Jul – 2 Aug, and Boston's Whales on Stellwagen Bank around 15 Apr – 20 Oct.