Surf Forecasts:
Trearddur Bay (Holy Island) surf forecast from 18 Aug 2026:
- Most powerful swell: Thursday 20 Aug, 1AM (local time) - 3.5ft (1.1m), 5s period, SW swell with 64 kJ wave energy.
Best Forecast Surf Conditions for Trearddur Bay (Holy Island) this week:
The most powerful waves expected at Trearddur Bay (Holy Island) in the next 16 days are 1.1m 5s and forecast to arrive on Thursday (Aug 20) at 1AM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.2m 5s period and expected on Friday (Aug 21) at 10PM.
| Wave Type | Time (BST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | - | - |
| Best Surf | - | - |
| Most Powerful | 1AM (Thu 20th Aug) | 3.5ft (1.1m) 5s |
Table - best surf conditions forecast for Trearddur Bay (Holy Island) over the next 16 days.
The Lowdown
Right folks, Rusty here. Let’s have a look at what’s cooking for Holy Island.
To be straight with you, this is a tough read. The whole 16-day window is a bit of a write-off for decent waves. We’ve got a long stretch of tiny, weak surf and messy wind, so don’t get your hopes up for any standouts. There’s a definite gap from now until late in the month where it’s just not worth paddling out.
The first bit of hope comes right at the very end, but it’s a long way off. For now, the water temp is sitting at 63°, which is a touch warmer than normal for this time of year, so at least it’s not freezing when you’re getting skunked.
We start with Trearddur Bay (Holy Island) on Tuesday afternoon, 18th August. It’s a measly 2ft of swell from the SW with a short period of 6 seconds, and the combined energy is weak (24). The wind is onshore, so it’s poor. Wednesday and Thursday don’t get any better – tiny, choppy, and messy. The end of the week and into the weekend sees the swell drop to almost nothing, with a long period of 14-15 seconds but only 0.3ft of height. That’s a ghost of a groundswell with no power (energy 8).
By the 24th, Monday morning, we get glassy conditions, but the swell is still barely a whisper at 0.3ft. It’s clean, but there’s nothing to ride. The pattern of poor conditions continues right through to the end of August. The wind is mostly cross or onshore, and the swell is tiny.
Now, look ahead to the end of the window. Our best bet, and I mean the only one that even gets a little interesting, is on Monday afternoon, the 31st of August. Swell picks up to 6ft from the SW at 6 seconds. The combined energy jumps to 303 (moderate). That’s a decent pulse of short-period swell. The problem is the wind is onshore from the SSW at 22 mph. At 6ft, it’s getting a bit too big for beginners. It won’t be pretty, but it’s the most power we’ll see. The following days, 1st and 2nd September, have similar size but with strong cross-onshore winds, making it choppy and messy.
Honestly, there’s no true standout here. The 31st of August has the most size, but the wind is rubbish. Keep an eye on the forecast, but for now, it’s a waiting game.
Rusty.
Short Range ForecastModerate rain (total 18mm), heaviest on Tue night. Very mild (max 17°C on Tue afternoon, min 13°C on Thu night). Mainly fresh winds. | Days 5-7 Weather SummaryMostly dry. Very mild (max 16°C on Mon morning, min 13°C on Fri night). Wind will be generally light. | |||||||||||||||||||
Tue 18 | Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | ||||||||||||||
PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | |
Swell Height Map |  |  |  |  |  |  |  | |||||||||||||
Wave Height (m) Direction Period (s) | SW 6 | W 4 | WSW 4 | SW 4 | SW 5 | SW 6 | SW 6 | SW 14 | SW 14 | SW 13 | SW 13 | SW 15 | SW 15 | SW 15 | SW 14 | SW 14 | SW 14 | SW 14 | SSW 3 | SW 4 |
Wave Graph  | ||||||||||||||||||||
 kJ | 16 | 18 | 24 | 16 | 64 | 18 | 10 | 8 | 7 | 7 | 7 | 8 | 8 | 8 | 8 | 7 | 8 | 8 | 8 | 20 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | cross-on | cross-on | on | cross-on | off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross | glassy | glassy | cross-on | cross-on |
High Tide | 3:07AM4.98m | 3:32PM4.68m | 3:52AM4.62m | 4:23PM4.44m | 4:52AM4.29m | 5:32PM4.26m | 6:23AM4.10m | 7:07PM4.27m | 8:04AM4.17m | 8:27PM4.49m | 9:08AM4.41m | 9:19PM4.79m | ||||||||
Low Tide | 8:54PM1.47m | 9:26AM1.59m | 9:39PM1.83m | 10:14AM1.98m | 10:37PM2.18m | 11:17AM2.31m | 11:58PM2.41m | 12:45PM2.45m | 1:37AM2.37m | 2:08PM2.34m | 2:47AM2.11m | 3:05PM2.09m | 3:35AM1.78m | |||||||
 |  |  | | | | |  |  |  |  | | | | | | | | | | |
 | — | — | 6:03 | — | — | 6:05 | — | — | 6:07 | — | — | 6:09 | — | — | 6:11 | — | — | 6:13 | — | — |
 | 8:40 | — | — | 8:37 | — | — | 8:36 | — | — | 8:34 | — | — | 8:31 | — | — | 8:29 | — | — | 8:27 | — |
mm | — | 6 | 1 | 1 | 6 | 3 | 1 | — | — | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 17 | 15 | 16 | 16 | 16 | 14 | 15 | 14 | 14 | 14 | 14 | 13 | 14 | 14 | 14 | 15 | 15 | 16 | 16 | 16 |
Feels °C | 14 | 12 | 13 | 11 | 13 | 9 | 10 | 10 | 9 | 9 | 9 | 10 | 10 | 11 | 12 | 13 | 14 | 15 | 15 | 15 |
Swell 1 Height (m) Direction Period (s) | NW 4 | — | SSW 6 | NW 4 | SW 16 | SW 6 | SW 6 | SSW 6 | SW 6 | SW 5 | SW 13 | SW 15 | SW 15 | SW 15 | SW 14 | N 4 | SW 14 | SW 14 | SW 14 | SW 13 |
| kJ | 8 | — | 4 | 2 | 10 | 18 | 10 | 4 | 1 | 1 | 7 | 8 | 8 | 8 | 8 | 6 | 8 | 8 | 7 | 7 |
Swell 2 Height (m) Direction Period (s) | — | — | SW 16 | S 15 | — | SW 15 | SW 14 | SW 14 | SW 14 | SW 13 | S 5 | — | — | S 12 | — | SW 14 | — | — | — | SW 13 |
| kJ | — | — | 10 | 5 | — | 8 | 8 | 8 | 7 | 7 | 1 | — | — | 3 | — | 7 | — | — | — | 7 |
Swell 3 Height (m) Direction Period (s) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| kJ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Wind waves Height (m) Direction Period (s) | SW 6 | W 4 | WSW 4 | SW 4 | SW 5 | NNW 4 | N 5 | N 4 | NNW 5 | NNW 4 | N 5 | NNW 5 | NNW 4 | N 5 | NNW 5 | WNW 3 | WSW 2 | SW 3 | SSW 3 | SW 4 |
| kJ | 16 | 18 | 24 | 16 | 64 | 29 | 49 | 33 | 32 | 30 | 53 | 22 | 16 | 43 | 25 | 2 | 1 | 2 | 8 | 20 |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 376 | 182 | 246 | 249 | 252 | 174 | 179 | 179 | 179 | 284 | 273 | 273 | 208 | 208 | 273 | 287 | 219 | 246 | 246 | 246 |
Best forecast wave conditions in Anglesy | ||||||||||||||||||||
Best forecast wave conditions in United Kingdom | ||||||||||||||||||||
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Information about the Trearddur Bay (Holy Island) Surf forecast
The above surf forecast table for Trearddur Bay (Holy Island) provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Trearddur Bay (Holy Island) can be found by selecting the local surf guide option on the grey menu. Our Trearddur Bay (Holy Island) 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 (Trearddur Bay (Holy Island)) 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 Trearddur Bay (Holy Island) 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.
Are you planning a holiday in Anglesy? If you are looking for accommodation near Trearddur Bay (Holy Island), camping, hotels and holiday cottages in Anglesy, consider staying in Holyhead which is 4 km (2 miles) away. Other places in and around Anglesy where you can find information about places to rent, and car hire include Anglesey which is 7 km (4 miles) away, Bangor, Porthmadog and Llandudno.
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