Best Time to Dive Guam
Across 6 Guam dive sites with multi-year conditions history, June historically shows the most favorable days — 87% of sampled days in the good band. The next-highest months are July (78%), September (73%) and May (73%). February historically shows the fewest favorable days (1% of sampled days). Average water temperature in the sample runs from about 28°C in February to 30°C in August. Typical seas range from 1.1 m to 2.2 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 Guam?
| Month | Historically favorable days | Water temp | Typical seas |
|---|---|---|---|
| Jan | 11% | 29°C | 2.2 m |
| Feb | 1% | 28°C | 2.2 m |
| Mar | 32% | 28°C | 1.9 m |
| Apr | 54% | 29°C | 1.5 m |
| May | 73% | 29°C | 1.5 m |
| Jun | 87% | 30°C | 1.1 m |
| Jul | 78% | 30°C | 1.3 m |
| Aug | 71% | 30°C | 1.3 m |
| Sep | 73% | 30°C | 1.4 m |
| Oct | 55% | 30°C | 1.6 m |
| Nov | 22% | 29°C | 1.8 m |
| Dec | 10% | 29°C | 2.0 m |
% = share of sampled days scoring in the favorable band, median across 6 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 Micronesia & western Pacific region — not site-specific promises.
- Whale sharkDec–Jan
- Scalloped hammerheadFeb–Mar
- Humpback whaleJul–Oct
- Reef manta rayJun–Sep
- Tiger sharkyear-round
- Bull sharkyear-round
- Green sea turtleyear-round
Bars are Jan–Dec — months when sightings historically concentrate (GBIF occurrence records). Wildlife is never guaranteed.
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