Surf Forecasts:
Ammonias surf forecast from 20 Aug 2026:
- Best quality surf: Thursday 20 Aug, 11PM (local time) - 2.5ft (0.7m), 16s period, SSW swell with cross-offshore winds.
- Most powerful swell: Thursday 27 Aug, 11AM (local time) - 3.5ft (1.1m), 17s period, S swell with 710 kJ wave energy.
- Next surfable swell (1★+): Thursday 20 Aug, 11PM (local time) - 2.5ft (0.7m), 16s period with SSW swell.
Best Forecast Surf Conditions for Ammonias this week:
The surf forecast for Ammonias over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Thursday (Aug 20) at 11PM. The primary swell is predicted to be 0.7m and 16s period with a secondary swell of 1.2m and 7s. The wind is predicted to be cross-offshore as the swell arrives.
The most powerful waves expected at Ammonias in the next 16 days are 1.1m 17s and forecast to arrive on Thursday (Aug 27) at 11AM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.1m 7s period and expected on Friday (Aug 21) at 5AM.
| Wave Type | Time (HST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 11PM (Thu 20th Aug) | 2.5ft (0.7m) 16s |
| Best Surf | 11PM (Thu 20th Aug) | 2.5ft (0.7m) 16s |
| Most Powerful | 11AM (Thu 27th Aug) | 3.5ft (1.1m) 17s |
Table - best surf conditions forecast for Ammonias over the next 16 days.
The Lowdown
Right then, let’s have a look at what’s cookin’ at Ammonias. It’s a reef break, and it’s got a decent SSE swell window. The water’s sittin’ at 80°, which is about normal for this time of year, so no surprises there.
Honestly, the next couple of weeks are a bit of a grind. We’ve got some energy bumpin’ through, but the winds are mostly cross or cross-on from the ENE or NE, which is gonna keep the surface a bit lumpy and chopped. The first real standout is a sniff of clean conditions on the morning of Friday, the 4th of September. We’ll see a moderate cross-off breeze from the NNE, which should clean up those 6ft waves with a period of 9 seconds. The combined swell energy will be solid at 747, so there’s a bit of push behind it. That’s a long way off though, so treat it as a promising one but don't book the day off yet.
Before that, there’s not a lot to get excited about. The swell is often messy with short-period windswell (6-7 seconds), or if it’s got a longer period from the SSW or S, it’s coming with a nasty cross-onshore wind. There’s a bit of a bump in size on Monday the 31st of August, with 6ft to 7ft of ENE groundswell (12-second period), giving a meaty combined energy of 1281 to 1407. But again, it’s got a fresh cross-shore wind, making it lumpy. For the average punter, that’s a bit of a handful, but for an expert on a reef, it could be interesting if the wind plays ball. It's also a fairly consistent spot so it won't be flat, but the quality is the issue.
If you’re a kiter, this whole period might look better than for a paddle surfer, with that persistent side wind and decent swell.
So, if you’re chasin’ the cleanest waves, set your alarm for the morning of Friday the 4th of September. That’s your best bet.
Rusty.
Short Range ForecastMostly dry. Warm (max 27°C on Thu afternoon, min 25°C on Thu morning). Wind will be generally light. | Days 4-6 Weather SummarySome drizzle, heaviest during Tue afternoon. Warm (max 27°C on Sun afternoon, min 25°C on Sun morning). Wind will be generally light. | ||||||||||||||||||||
Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | Wednesday 26 | |||||||||||||||
AM | 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) | SSW 18 | SSW 17 | SW 16 | SSW 17 | SW 16 | SSW 16 | SW 16 | SW 16 | ENE 7 | E 7 | E 7 | ENE 7 | SSW 14 | SSW 13 | ENE 6 | E 6 | E 7 | ENE 7 | S 18 | S 18 | S 18 |
Wave Graph  | |||||||||||||||||||||
 kJ | 207 | 195 | 278 | 255 | 258 | 322 | 261 | 251 | 268 | 345 | 355 | 277 | 194 | 156 | 145 | 232 | 233 | 197 | 231 | 404 | 429 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross | cross | cross | on | on | cross | cross-on | cross | cross | cross | cross | cross | cross | cross | cross | cross-on | cross | cross-on | cross-on | cross | cross |
High Tide | 11:20AM0.53m | 12:20PM0.56m | 11:30PM0.20m | 1:07PM0.59m | 00:35AM0.22m | 1:46PM0.62m | 1:16AM0.25m | 2:19PM0.63m | 1:51AM0.28m | 2:48PM0.64m | 2:25AM0.31m | 3:14PM0.64m | 3:02AM0.35m | ||||||||
Low Tide | 3:21AM0.10m | 9:24PM0.19m | 9:13PM0.18m | 5:45AM0.08m | 9:16PM0.18m | 6:37AM0.05m | 9:23PM0.17m | 7:21AM0.04m | 9:34PM0.16m | 8:01AM0.03m | 9:50PM0.13m | ||||||||||
 | |  | | | |  | | | | | | | |  | |  | |  | |  | |
 | 6:16 | — | — | 6:16 | — | — | 6:16 | — | — | 6:16 | — | — | 6:16 | — | — | 6:18 | — | — | 6:18 | — | — |
 | — | 7:04 | — | — | 7:02 | — | — | 7:01 | — | — | 7:01 | — | — | 7:00 | — | — | 7:00 | — | — | 6:59 | — |
mm | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | — | — | — | — |
Temp °C | 26 | 27 | 25 | 27 | 27 | 26 | 26 | 27 | 25 | 26 | 27 | 25 | 26 | 26 | 25 | 26 | 26 | 25 | 25 | 26 | 24 |
Feels °C | 28 | 29 | 27 | 30 | 30 | 30 | 27 | 28 | 26 | 26 | 27 | 25 | 26 | 26 | 25 | 26 | 26 | 26 | 25 | 25 | 24 |
Swell 1 Height (m) Direction Period (s) | E 8 | NE 7 | ENE 7 | ENE 7 | SW 16 | SSW 16 | SW 16 | SW 16 | SSW 16 | SSW 15 | SSW 15 | SSW 14 | SSW 14 | SSW 13 | SSW 12 | SSW 16 | SSW 16 | SSE 9 | SSW 14 | S 18 | S 18 |
| kJ | 60 | 79 | 142 | 57 | 258 | 322 | 261 | 251 | 212 | 196 | 188 | 183 | 163 | 156 | 121 | 201 | 140 | 52 | 215 | 404 | 429 |
Swell 2 Height (m) Direction Period (s) | SSW 18 | SSW 17 | SW 16 | SSW 17 | ENE 7 | W 10 | W 10 | W 11 | WNW 11 | S 13 | WNW 11 | SE 11 | SE 10 | SE 10 | SE 9 | SE 9 | SSE 9 | SSW 15 | S 18 | SSW 13 | SSW 13 |
| kJ | 207 | 195 | 278 | 255 | 43 | 50 | 78 | 83 | 100 | 130 | 51 | 75 | 63 | 76 | 46 | 41 | 54 | 167 | 231 | 133 | 135 |
Swell 3 Height (m) Direction Period (s) | SSE 10 | W 10 | WSW 9 | NE 7 | NE 7 | SSE 14 | S 14 | SE 8 | S 14 | WNW 12 | SE 10 | S 13 | S 13 | SSE 12 | SSW 16 | SSW 12 | SSW 12 | S 18 | SSE 7 | SE 9 | SE 8 |
| kJ | 36 | 50 | 26 | 49 | 37 | 62 | 107 | 17 | 107 | 53 | 36 | 89 | 87 | 28 | 105 | 83 | 86 | 167 | 19 | 38 | 17 |
Wind waves Height (m) Direction Period (s) | NE 7 | — | — | — | — | ENE 7 | ENE 7 | ENE 6 | ENE 7 | E 7 | E 7 | ENE 7 | ENE 6 | ENE 6 | ENE 6 | E 6 | E 7 | ENE 7 | ENE 6 | ENE 7 | ENE 6 |
| kJ | 61 | — | — | — | — | 102 | 117 | 156 | 268 | 345 | 355 | 277 | 194 | 144 | 145 | 232 | 233 | 197 | 176 | 158 | 121 |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 12 | 12 | 10 | 33 | 32 | 10 | 31 | 16 | 16 | 31 | 38 | 31 | 16 | 16 | 16 | 31 | 16 | 16 | 31 | 16 | 16 |
Best forecast wave conditions in Kaua'i | |||||||||||||||||||||
Best forecast wave conditions in United States | |||||||||||||||||||||
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Information about the Ammonias Surf forecast
The above surf forecast table for Ammonias provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Ammonias can be found by selecting the local surf guide option on the grey menu. Our Ammonias 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 (Ammonias) 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 Ammonias 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 vacation in Kaua'i? If you are looking for accommodation near Ammonias, camping, hotels and condos and appartments in Kaua'i, consider staying in Nawiliwili which is 2 km (1 miles) away. Alternatively, find information about places to stay and car hire in Lihue - Kauai which is 3 km (2 miles) away
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