Best Time to Dive Massachusetts
Across 30 Massachusetts dive sites with multi-year conditions history, July historically shows the most favorable days — 90% of sampled days in the good band. The next-highest months are August (85%), June (83%) and September (77%). January historically shows the fewest favorable days (34% of sampled days). Average water temperature in the sample runs from about 4°C in February to 20°C in August. Typical seas range from 0.6 m to 1.3 m of significant wave height through the year. These figures are historical climatology computed from measured conditions — patterns, not a forecast or a guarantee.
Computed from our own conditions climatology — measured history, not brochure copy.
Which months are historically most favorable in Massachusetts?
| Month | Historically favorable days | Water temp | Typical seas |
|---|---|---|---|
| Jan | 34% | 5°C | 1.3 m |
| Feb | 36% | 4°C | 1.2 m |
| Mar | 35% | 5°C | 1.3 m |
| Apr | 59% | 7°C | 1.0 m |
| May | 70% | 12°C | 0.9 m |
| Jun | 83% | 17°C | 0.7 m |
| Jul | 90% | 20°C | 0.6 m |
| Aug | 85% | 20°C | 0.7 m |
| Sep | 77% | 19°C | 0.9 m |
| Oct | 60% | 15°C | 1.1 m |
| Nov | 43% | 11°C | 1.1 m |
| Dec | 38% | 8°C | 1.2 m |
% = share of sampled days scoring in the favorable band, median across 30 dive sites with at least two years of history. Ringed = historical peak.
How does this compare worldwide? The Most Reliable Diving Months on Earth ranks 61 countries by the same measure.
Marine life seasons
Sighting patterns across the wider US & Canada — Atlantic coast region — not site-specific promises.
- Scalloped hammerheadAugust
- Great white sharkAug–Sep
- Giant oceanic manta rayJul–Sep
- OrcaMay–Aug
- Humpback whaleJun–Aug
Bars are Jan–Dec — months when sightings historically concentrate (GBIF occurrence records). Wildlife is never guaranteed.
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