INSTRUMENT / SEA TEMPERATURE
Tumon Bay Water Temperature
Updated Tue 14:51 (Pacific/Guam)
Guam · Forecast updated Nov 10, 2026, 14:51 UTC
Current Sea Temperature
29.2°C
84.6°F
Very warm water
Valid Nov 10, 2026, 14:51 (Pacific/Guam). Source: stored Open-Meteo marine forecast. Temperature is not a safety rating or snorkel score.
Versus this month's average
Close to average
The typical November average is 29.4°C (84.9°F) from the historical baseline.
Recent trend
Warming by 0.3°C
Seven-day average: 29.2°C, versus 28.9°C in the prior seven days.
What to wear
Very warm water
Swimwear is usually enough; a rash guard adds sun protection.
Cold tolerance varies. Wind, session length, sunshine, and exertion also affect comfort; temperature alone does not describe sea conditions or replace the snorkel forecast.
Typical Sea Temperature Over the Year
In the historical baseline for Tumon Bay, typical monthly averages range from about 28.1°C (82.6°F) in February to 30.1°C (86.2°F) in August.
Over the past 30 days, the average sea temperature in Tumon Bay has been 29.0°C.
Historical baseline (full year)
Northern Hemisphere. Summer is generally June–August; winter is December–February.
Typical monthly sea-surface temperature near Tumon Bay, calculated from hourly observations for 2023–2025. This is not this site's forecast archive.
| Month | Typical range | Average |
|---|---|---|
| January | 28.6–28.8°C | 28.7°C / 83.7°F |
| February | 27.9–28.4°C | 28.1°C / 82.6°F |
| March | 28.0–28.5°C | 28.3°C / 82.9°F |
| April | 28.4–28.8°C | 28.6°C / 83.5°F |
| May | 29.0–29.3°C | 29.1°C / 84.4°F |
| June | 29.0–29.9°C | 29.5°C / 85.1°F |
| July | 29.7–30.0°C | 29.8°C / 85.6°F |
| August | 29.8–30.4°C | 30.1°C / 86.2°F |
| September | 29.8–30.1°C | 29.9°C / 85.8°F |
| October | 29.6–29.9°C | 29.8°C / 85.6°F |
| November | 29.4–29.4°C | 29.4°C / 84.9°F |
| December | 29.1–29.2°C | 29.1°C / 84.4°F |
Source: Open-Meteo Marine API, MeteoFrance sea-surface temperature dataset. Nearest sea grid cell (13.54, 144.79). Each month is the mean of yearly monthly means; the range is the lowest and highest of those yearly monthly means. Open-Meteo methodology.
Water temperature by month
Each month uses the 2023–2025 baseline. The range is the lowest and highest yearly monthly mean, not an hourly extreme.
Tumon Bay in January
Typical January water temperature near Tumon Bay is 28.7°C (83.7°F), with yearly monthly means from 28.6–28.8°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: December 29.1°C · February 28.1°C.
Explore Tumon Bay sea temperature in January, including swim comfort and month comparisons →
Tumon Bay in February
Typical February water temperature near Tumon Bay is 28.1°C (82.6°F), with yearly monthly means from 27.9–28.4°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: January 28.7°C · March 28.3°C.
Explore Tumon Bay sea temperature in February, including swim comfort and month comparisons →
Tumon Bay in March
Typical March water temperature near Tumon Bay is 28.3°C (82.9°F), with yearly monthly means from 28.0–28.5°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: February 28.1°C · April 28.6°C.
Explore Tumon Bay sea temperature in March, including swim comfort and month comparisons →
Tumon Bay in April
Typical April water temperature near Tumon Bay is 28.6°C (83.5°F), with yearly monthly means from 28.4–28.8°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: March 28.3°C · May 29.1°C.
Explore Tumon Bay sea temperature in April, including swim comfort and month comparisons →
Tumon Bay in May
Typical May water temperature near Tumon Bay is 29.1°C (84.4°F), with yearly monthly means from 29.0–29.3°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: April 28.6°C · June 29.5°C.
Explore Tumon Bay sea temperature in May, including swim comfort and month comparisons →
Tumon Bay in June
Typical June water temperature near Tumon Bay is 29.5°C (85.1°F), with yearly monthly means from 29.0–29.9°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: May 29.1°C · July 29.8°C.
Explore Tumon Bay sea temperature in June, including swim comfort and month comparisons →
Tumon Bay in July
Typical July water temperature near Tumon Bay is 29.8°C (85.6°F), with yearly monthly means from 29.7–30.0°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: June 29.5°C · August 30.1°C.
Explore Tumon Bay sea temperature in July, including swim comfort and month comparisons →
Tumon Bay in August
Typical August water temperature near Tumon Bay is 30.1°C (86.2°F), with yearly monthly means from 29.8–30.4°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: July 29.8°C · September 29.9°C.
Explore Tumon Bay sea temperature in August, including swim comfort and month comparisons →
Tumon Bay in September
Typical September water temperature near Tumon Bay is 29.9°C (85.8°F), with yearly monthly means from 29.8–30.1°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: August 30.1°C · October 29.8°C.
Explore Tumon Bay sea temperature in September, including swim comfort and month comparisons →
Tumon Bay in October
Typical October water temperature near Tumon Bay is 29.8°C (85.6°F), with yearly monthly means from 29.6–29.9°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: September 29.9°C · November 29.4°C.
Explore Tumon Bay sea temperature in October, including swim comfort and month comparisons →
Tumon Bay in November
Typical November water temperature near Tumon Bay is 29.4°C (84.9°F), with yearly monthly means from 29.4–29.4°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: October 29.8°C · December 29.1°C.
Explore Tumon Bay sea temperature in November, including swim comfort and month comparisons →
Tumon Bay in December
Typical December water temperature near Tumon Bay is 29.1°C (84.4°F), with yearly monthly means from 29.1–29.2°C.
Swimming and snorkeling: very warm water. Swimwear is usually enough; a rash guard adds sun protection.
Adjacent months: November 29.4°C · January 28.7°C.
Explore Tumon Bay sea temperature in December, including swim comfort and month comparisons →
Forecast archive (growing)
These values come from hourly forecasts SnorkelForecast has stored. They cover only months with records and do not replace the historical baseline.
| Month | Min | Average | Max |
|---|---|---|---|
| June | 29.0°C / 84.2°F | 29.7°C / 85.5°F | 30.6°C / 87.1°F |
| July | 28.8°C / 83.8°F | 29.4°C / 84.9°F | 30.4°C / 86.7°F |
| August | 29.3°C / 84.7°F | 29.5°C / 85.2°F | 30.2°C / 86.4°F |
| September | 29.2°C / 84.6°F | 29.8°C / 85.6°F | 30.6°C / 87.1°F |
| October | 28.1°C / 82.6°F | 29.1°C / 84.4°F | 30.1°C / 86.2°F |
| November | 28.8°C / 83.8°F | 29.3°C / 84.7°F | 29.7°C / 85.5°F |
Partial coverage: 6 calendar months with records. Profile calculated from 3911 hourly forecast records across 6 monthly periods. This is a growing archive, not a long-term climate normal.
About the water at Tumon Bay
Protected preserve with shallow reef and reef fish off the main beach strip.
- Area
- Guam
Tumon Bay Water Temperature: Common Questions
What is the water temperature in Tumon Bay today?
The current sea surface temperature near Tumon Bay is 29.2°C (84.6°F). Over the last 30 days, the average has been 29.0°C.
When is the water warmest in Tumon Bay?
The water is typically warmest in August, at around 30.1°C (86.2°F) in the 2023–2025 historical baseline.
When is the water coldest in Tumon Bay?
The water is typically coldest in February, at around 28.1°C (82.6°F) in the same historical baseline.
Can you swim in Tumon Bay today?
At 29.2°C, the water is usually comfortable for swimming and snorkeling.
Full Snorkeling Forecast
See how today's sea temperature, wave height, wind, and tides combine into a detailed snorkeling score for Tumon Bay.
View Snorkel Forecast →