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Chesil wave buoy daily means for Sep 2025

Daily means from the Chesil 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

1,438 wave-buoy observations covered all 30 days. Typical wave height was 3.6 ft (10th–90th percentile 1.1–7.3 ft), while mean average of more than one wave period type was 7.5 seconds (10th–90th percentile 5–10.5 seconds). Mean water temperature was 17.4°C (10th–90th percentile 16.1–18.6°C). 4 of 5,701 checked values (0.1%) were excluded by quality control. Across 15 comparable years, mean wave height was above the same-month mean of 2.6 ft and mean wave period was below the same-month mean of 7.6 seconds.

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

Typical Significant Wave Height

3.6ft
Mean: 3.9 ft
P10–P90: 1.1 — 7.3 ft
Recorded extremes

0.6 — 11.1 ft

Available for 719 of 720 hourly samples

Mean Observed Wave Period

7.5secs
P10–P90: 5 — 10.5secs
Recorded extremes

2.6 — 16.7secs

Available for 719 of 720 hourly samples

Observed Wave Direction

SSW

Circular concentration: 93%

Mean Water Temperature

17.4°C
P10–P90: 16.1 — 18.6°C
Recorded extremes

15.9 — 18.8°C

Available for 719 of 720 hourly samples

Compared With Previous Septembers

Historical baseline from 21,543 observations across 15 years.

Wave Height
3.9ft
1.3ft above mean
Historical mean 2.625ft
Wave Period
7.5s
0.1s below mean
Historical mean 7.6s
Water Temperature
17.4°C
In line with the historical mean
Historical mean 17.4°C

Chart showing grouped wave observations for Chesil. 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 Chesil wave buoy

Chesil is a Channel Coastal Observatory National Network wave station off Dorset's exposed Jurassic Coast. It records waves approaching Chesil Beach and the western side of Portland, providing a nearshore reference for the long shingle barrier and the communities and infrastructure behind it.

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

Metrics are rows; days run left to right.
Chesil wave buoy daily means Sep 2025Last observation shown
Metric
Mean significant wave height (ft)658632344566559575242111112311
Mean maximum wave height (ft)971310545767101088158117463222223422
Mean peak period (s)6671086796666678666988689975111210
Mean zero-crossing period (s)545544454455556554546555653565
Mean energy period (s)------------------------------
Mean wave power, kilowatts per metre------------------------------
Mean peak wave directionSWconcentration 100%SWconcentration 99%SWconcentration 100%SWconcentration 100%SWconcentration 100%Sconcentration 93%SSWconcentration 93%SWconcentration 100%SWconcentration 99%SWconcentration 99%SWconcentration 100%SWconcentration 100%SWconcentration 100%SWconcentration 97%SWconcentration 100%SWconcentration 100%SWconcentration 100%SWconcentration 100%SWconcentration 99%SWconcentration 99%SWconcentration 99%Sconcentration 96%SSEconcentration 91%Sconcentration 93%SSWconcentration 86%Sconcentration 90%Sconcentration 96%SSWconcentration 98%SWconcentration 99%SWconcentration 97%
Mean directional spread (°)21.522.418.317.429.131.929.522.126.221.917.318.919.725.915.619.519.721.841.430.739.536.341.545.549.640.529.046.456.061.5
Mean water temperature(°C)18.718.618.618.518.518.518.418.418.418.218.017.617.517.317.117.016.916.917.117.116.916.716.516.416.316.116.116.016.116.1

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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 Regional Coastal Monitoring Programme.

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

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