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The Knap Surf Forecast
/ Wales – South East (14 surf breaks) /
Surf Forecasts:
The Knap surfForecast / Wales – South East / UK
12 Day Weather and Surf, issued 12 am Thursday 18 Sep 2025 BST
Best Forecast Surf Conditions for The Knap this week:
The most powerful waves expected at The Knap in the next 12 days are 0.6m 12s and forecast to arrive on Thursday (Sep 18) at 7AM. Winds are predicted to be onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.4m 3s period and expected on Monday (Sep 22) at 10AM.
| Wave Type | Time (BST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | - | - |
| Best Surf | - | - |
| Most Powerful | 7AM (Thu 18th Sep) | 2ft (0.6m) 12s |
Table - best surf conditions forecast for The Knap over the next 12 days.
Short Range Forecast Mostly dry. Warm (max 21°C on Thu morning, min 14°C on Fri night). Wind will be generally light. | Days 3-6 Weather Summary Light rain (total 7mm), mostly falling on Sun morning. Very mild (max 17°C on Sat night, min 9°C on Mon night). Winds decreasing (fresh winds from the NE on Mon afternoon, light winds from the NW by Tue afternoon). | |||||||||||||||||||||
Thursday 18 | Friday 19 | Saturday 20 | Sunday 21 | Monday 22 | Tuesday 23 | Wed 24 | ||||||||||||||||
| Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | ||
Rating (10 max) | ||||||||||||||||||||||
Swell Height Map |  |  |  |  |  |  |  |  | ||||||||||||||
| Wave Height (m) & direction (?) | — | — | ||||||||||||||||||||
| Period(s) (?) | 12 | 12 | 11 | 10 | 9 | 10 | 10 | 9 | 9 | 9 | 8 | 8 | 7 | 6 | 4 | 3 | - | - | 4 | 12 | 11 | |
Wave (?)Graph  | ||||||||||||||||||||||
 kJ (?) | 152 | 72 | 63 | 33 | 29 | 31 | 18 | 14 | 6 | 6 | 7 | 6 | 1 | 1 | 0 | 0 | 0 | 0 | 2 | 3 | 2 | |
Wind (km/h) | ||||||||||||||||||||||
| Wind State (?) onshore cross-onshore cross-shore cross-offshore offshore glassy | cross- on | on | cross- on | on | cross- on | on | glass | cross | cross- on | on | cross- on | cross- on | cross- off | cross- off | cross- off | off | off | off | off | cross- off | glass | |
High Tide / height (m) | 4:59AM 8.61 | 5:28PM 9.28 | 5:59AM 9.36 | 6:20PM 10.06 | 6:44AM 10.10 | 7:01PM 10.75 | 7:22AM 10.71 | 7:37PM 11.27 | 7:56AM 11.15 | 8:11PM 11.56 | 8:27AM 11.39 | 8:42PM 11.64 | 8:57AM 11.41 | |||||||||
Low Tide / height (m) | 10:55PM 3.79 | 11:24AM 3.66 | 12:01AM 3.06 | 12:18PM 2.91 | 12:45AM 2.34 | 12:58PM 2.22 | 1:19AM 1.75 | 1:30PM 1.65 | 1:49AM 1.31 | 2:00PM 1.24 | 2:17AM 1.03 | 2:29PM 1.02 | 2:45AM 0.93 | 2:57PM 0.99 | ||||||||
Thursday 18 | Friday 19 | Saturday 20 | Sunday 21 | Monday 22 | Tuesday 23 | Wed 24 | ||||||||||||||||
| Sunrise | - | 6:50 | - | - | 6:52 | - | - | 6:54 | - | - | 6:56 | - | - | 6:58 | - | - | 6:58 | - | - | 7:01 | - | |
| Sunset | - | - | 7:22 | - | - | 7:19 | - | - | 7:16 | - | - | 7:15 | - | - | 7:12 | - | - | 7:09 | - | - | 7:07 | |
 |  |  |  | | | | | | |  | |  |  | |  | | | | | | ||
Rain (mm) | - | - | - | - | - | - | - | - | - | - | 2 | 2 | 2 | 1 | - | - | - | - | - | - | - | |
| Temp. °C | 18 | 21 | 21 | 17 | 20 | 21 | 16 | 19 | 20 | 17 | 16 | 16 | 14 | 14 | 15 | 12 | 13 | 15 | 13 | 12 | 14 | |
| Feels °C (?) | 15 | 19 | 19 | 16 | 18 | 19 | 16 | 18 | 18 | 14 | 10 | 11 | 11 | 8 | 8 | 6 | 8 | 12 | 10 | 9 | 12 | |
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Live Wave Height (m)
Live Wind Speed (km/h)
Surf Rating (10 Max)
Ocean Swells (m)- Wind Speed (km/h)
Recent Eyeball Surf Reports for Wales - South East
The wind is still cross-on at The Knap (light winds from the W at Cardiff-Wales Airport 4 km from The Knap). 0.8m 7s swell from the W with a 0.5m 12s groundswell, also from the W. 2 swells combining to make bigger set waves.
2 h 9 min ago
FREE! Surf-Forecast.com widget for your website
The surf report / weather widget below is available to embed on third party websites free of charge and provides a summary of our The Knap surf forecast. Simply grab the html code snippet that we provide and paste it into your own site. You can choose your preferred language and metric/imperial units for the surf forecast feed to suit users of your site. Click here to get the code.
Information about the The Knap Surf forecast
The above surf forecast table for The Knap provides essential information for determining whether the surfing conditions will be good over the next 12 days. A general guide to surfing at The Knap can be found by selecting the local surf guide option on the grey menu. Our The Knap surf forecast is unique since it includes wave energy (power) that defines the real feel of the surf rather than just the height or the period. If you surf the same spot (The Knap) regularly then make a mental note of the wave energy from the surf forecast table each time you go. Very soon you may start to choose your surf days based on the wave energy alone combined with our forecast of favourable offshore wind conditions. Our star ratings will help here and of course you will also find the usual wave height and period predictions on our surf forecasts as well as a full break down of the swell components under our advanced users option (to reveal that, click the little Einstein character under the tide times).
Further information to help with frequently asked questions about our surf forecast for The Knap may be found under the help tab on the top menu and also by moving your mouse over the question marks on the surf forecast table itself. Please always bear in mind that the forecast is for near-shore open water and local factors at each surf break influence the actual breaking wave height, such as the beach / reef profile, water depths offshore and shelter.
The Knap is 2 km (1 miles) from Barry. If you plan a holiday in Wales - South East, look for hotels and other accommodation in Barry. Barry has rooms for a wide range of budgets as well as car hire and transport links.
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