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Belle-Île wave buoy daily means for Sep 2025

Daily means from the Belle-Île wave buoy for Sep 2025, including available wave height, period, direction, wind and sea temperature data.

Last observation shown

Data available:  to 

Monthly means for

Latest

Period Summary

Programmatically generated summary. Hog Says

1,396 wave-buoy observations covered all 30 days. Typical wave height was 5.9 ft (10th–90th percentile 2.4–10.5 ft), while mean average of more than one wave period type was 9.8 seconds (10th–90th percentile 7.9–11.8 seconds). Typical calculated wave power was approximately 12 kW/m (10th–90th percentile 1.9–41.7 kW/m), derived from significant wave height and energy period. 3 of 4,056 checked values (0.1%) were excluded by quality control. Across 14 comparable years, mean wave height was above the same-month mean of 4.6 ft and mean wave period was the same as the same-month mean of 9.8 seconds.

Generated only from the observations and comparisons shown on this page.

Typical Significant Wave Height

5.9ft
Mean: 6.3 ft
P10–P90: 2.4 — 10.5 ft
Recorded extremes

1.6 — 16.2 ft

Mean Observed Wave Period

9.8secs
P10–P90: 7.9 — 11.8secs
Recorded extremes

3.2 — 15.6secs

Typical Wave Power

Approximately 11.99kW/m
Mean: 17.71kW/m
P10–P90: 1.94 — 41.7kW/m
Recorded extremes

0.65 — 113.28kW/m

Calculated from significant wave height and energy period.

Available for 641 of 702 hourly samples with wave power

Typical Observed Wind

-, -mph
Mean: - mph
P10–P90: - — - mph

Available for 0 of 702 hourly samples

Mean Water Temperature

-°C
P10–P90: - — -°C

Available for 0 of 702 hourly samples

Compared With Previous Septembers

Historical baseline from 20,152 observations across 14 years.

Wave Height
6.3ft
1.7ft above mean
Historical mean 4.56ft
Wave Period
9.8s
In line with the historical mean
Historical mean 9.8s
Water Temperature
–
Not enough comparable data

Chart showing grouped wave observations for Belle-Île. Use the table on this page for a text version of the same measurements. To open hourly observations, use a linked day name in the table.

About Belle-Île wave buoy

Belle-Île is a CANDHIS directional buoy south of Brittany, maintained through the Cerema-coordinated sea-state observatory and research partners. Its open Atlantic position represents conditions approaching Belle-Île and the sheltered-to-exposed transition along the Morbihan coast.

Its current data source reports wave height, wave period, wave direction, directional spread and sea temperature.

Metrics are rows; days run left to right.
Belle-Île wave buoy daily means Sep 2025Last observation shown
Metric
Mean significant wave height (ft)1010121164666810988111067556422323443
Mean maximum wave height (ft)16162017969109131514131318159108810634444764
Mean peak period (s)12911111099109910111110111210111088861110101112109
Mean average period (s)1099997898889889119109786578991099
Mean period Tm02 (s)878775676677667878766545576867
Mean peak wave directionWconcentration 100%Wconcentration 99%WSWconcentration 100%Wconcentration 100%Wconcentration 100%WSWconcentration 77%SWconcentration 74%Wconcentration 99%Wconcentration 99%Wconcentration 99%Wconcentration 100%WNWconcentration 100%WNWconcentration 100%Wconcentration 98%Wconcentration 100%Wconcentration 100%WNWconcentration 100%Wconcentration 100%Wconcentration 100%Wconcentration 99%Wconcentration 99%WNWconcentration 97%NWconcentration 54%WNWconcentration 99%Wconcentration 100%WNWconcentration 100%Wconcentration 100%Wconcentration 98%Wconcentration 100%Wconcentration 100%
Mean directional spread (°)25.832.326.226.127.332.532.230.830.029.927.125.627.331.226.426.229.028.029.532.130.332.337.934.931.731.135.034.533.131.5
Mean water temperature(°C)------------------------------

Swipe sideways to see more days.

Wave metric colour key

Colours move through the scale as each number increases. They do not by themselves mean that conditions are good, safe or suitable for you.

Wave & swell height0–40+ ft
Wave & swell period0–22+ s
Wind speed0–75 mph

The displayed numbers remain the source of truth; colour is an additional visual cue.

What does buoy wave power mean?

kW/m means kilowatts of wave power per metre of wave crest. It describes the rate at which the observed sea state carries energy past the buoy.

Unlike the shore-directed forecast value, buoy wave power is the total power at the observation point. It is not projected towards a particular beach and does not predict breaking wave height.

In deep water, wave power can be calculated with:

P is approximately 0.49 times significant wave height squared times wave energy period.

P is power in kW/m, Hs is significant wave height in metres, and Te is wave energy period in seconds.

  • Provider-reported power is used when available.
  • Otherwise, a value is calculated only when both significant height and a genuine energy period are available. The ≈ symbol marks calculated values.
  • A dash is shown instead of substituting peak, Tm02, zero-crossing or other period measurements.
  • Daily and monthly figures use the mean of hourly-normalized observation power values; they are not calculated from mean height and period.

Wave direction, spectrum, water depth and local bathymetry still matter. Wave power is best read alongside height, period and direction rather than as a standalone surf-quality score.

The observation data displayed on this page is from the Cerema CANDHIS coastal wave observatory.

Learn how SurfHog combines, checks and summarizes observations in the data and methodology notes.

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