Grandma's Surf Break

Lat Long: 20.79° N 156.56° W

Grandma's Surf Forecast and Surf Report

Issued: 1 pm 15 Sep 2026 (local time)

Forecast update in  hr  min

Today's Grandma's sea temperature is
27.1°C
0.2° 

Grandma's surf forecast is for near shore open water. Breaking waves will often be smaller at less exposed spots.


Grandma's surf forecast from 16 Sep 2026:

  • Best quality surf: Tuesday 15 Sep, 8PM (local time) - 2ft (0.6m), 19s period, SW swell with cross-offshore winds.
  • Most powerful swell: Friday 18 Sep, 2AM (local time) - 3ft (0.9m), 18s period, SSW swell with 541 kJ wave energy.
  • Next surfable swell (1★+): Tuesday 15 Sep, 8PM (local time) - 2ft (0.6m), 19s period with SW swell.

Best Forecast Surf Conditions for Grandma's this week:

The surf forecast for Grandma's over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Tuesday (Sep 15) at 8PM. The primary swell is predicted to be 0.6m and 19s period. The wind is predicted to be cross-offshore as the swell arrives.

The most powerful waves expected at Grandma's in the next 16 days are 0.9m 18s and forecast to arrive on Friday (Sep 18) at 2AM. Winds are predicted to be offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 2.5m 9s period and expected on Tuesday (Sep 22) at 2PM.

Wave TypeTime (HST) & Date Wave Height & Period
Next good surf (1 star+) 8PM (Tue 15th Sep)2ft (0.6m) 19s
Best Surf 8PM (Tue 15th Sep)2ft (0.6m) 19s
Most Powerful 2AM (Fri 18th Sep)3ft (0.9m) 18s

Table - best surf conditions forecast for Grandma's over the next 16 days.


The Lowdown

Alright folks, let's have a chat about what's coming up at Grandma's. We've got a bit of a mixed bag here, but there are definitely some windows to get a few clean ones.

The general vibe for the next couple of weeks is consistent but small. We're looking at a fairly steady run of knee- to waist-high swell, mostly from the SSW and SW. It's not going to blow you away, but for a little reef setup, there's plenty of life in it.

Let's kick things off. The best bet, and the standout of the whole run, comes together on Thursday, September 17th and into Friday, September 18th. Thursday morning we've got clean 2ft swell from the SW, and it's dead glassy with no wind at all. That is going to be smooth as silk. The water is sitting at a warm 81°, which is bang on average for this time of year, so no need for a wetsuit. The swell energy is moderate at 360 and 361. Then on Friday morning we see a little bump to 3ft, still glassy and clean. That window from Thursday morning right through Friday afternoon is where you want to be in the water. Expect good surf conditions, just keep in mind that Grandma's can get a bit crowded, so get in early.

From Saturday the 19th through to the end of the month, the consistency holds, but the quality dips in and out. Saturday afternoon looks good for a paddle with clean 2ft swell and a gentle offshore breeze from the NE, which will keep the surface tidy. However, by Monday the 21st, the swell period starts to drop, and the conditions become more ordinary. We see the combined energy drop from the 300s down into the 100s and 200s, and the reports change from "expect good surf" to "surfable but very ordinary."

There's a rough patch on the 23rd and 24th of September where we get onshore winds and poor conditions. Keep the board in the car those days.

Now, the second week holds some promise, but it's more of a watch-and-see. The period around Saturday, September 26th and Sunday, September 27th looks interesting again. We see the swell energy pick back up into the 300s and 380s, with clean glassy mornings and gentle offshores on the afternoons. The swell is still small, around 2ft to 3ft from the SSW and SW, but with that long-period groundswell (15-18 seconds), you'll get proper shape and more power behind each wave. Remember though, that long period stuff can make a beach break a bit straight, but for a little reef like Grandma's, it should link up nicely.

The very end of the month, Monday the 28th and Tuesday the 29th, is actually a real contender. We've got decent alignment: 2ft to 3ft swell from the SSW and SW, combined energy in the high 300s (389 and 395), and clean offshore winds from the NE all day. That's a solid setup for a long, cruisy session.

In summary, don't sleep on the Thursday and Friday of this week for the cleanest, glassiest waves. The following weekend looks promising too, but it's further out so keep an eye on it. For the most part, you'll find surfable waves, but you'll have to pick your moments around the wind.

Right, that's my two cents. Get amongst it.

Rusty

Short Range Forecast

Moderate rain (total 12mm), heaviest on Thu afternoon. Warm (max 29°C on Wed afternoon, min 25°C on Thu night). Wind will be generally light.

Days 5-7 Weather Summary

Mostly dry. Warm (max 29°C on Fri afternoon, min 25°C on Sat night). Wind will be generally light.

Tue
15
Wednesday
16
Thursday
17
Friday
18
Saturday
19
Sunday
20
Monday
21
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
Rating
(10 max)
2
2
2
1
2
2
2
2
2
1
2
2
2
2
2
2
1
1
1
1
Swell
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Wave
Height (m)
Direction
Period (s)
0.6
SSW
19
0.6
SW
19
0.7
SW
18
0.7
SW
18
0.7
SW
17
0.7
SW
16
0.7
SW
16
0.9
SSW
18
0.8
SSW
17
0.8
SSW
17
0.7
SW
16
0.8
SSW
16
0.6
SW
16
0.6
SSW
15
0.7
SSW
15
0.8
SSW
15
0.7
SSW
14
0.7
SSW
14
0.7
SSW
13
0.6
S
13
Wave Graph
Metric surfscale
Energy kJ
251
296
319
316
302
261
264
541
377
368
261
334
206
156
237
296
210
195
184
125
Wind (km/h)
0
SE
5
N
15
N
25
NNE
20
NNE
0
NNW
0
W
10
NNE
0
NNE
15
E
5
N
5
NW
15
NE
10
NNE
5
NNE
10
NNE
10
N
5
NNE
10
NNE
15
NNE
Wind State
glassy
cross-off
cross-off
cross-off
off
glassy
glassy
off
glassy
cross-off
cross-off
glassy
off
off
cross-off
cross-off
cross-off
cross-off
off
cross-off
High Tide
6:29PM0.37m
8:00AM0.66m
7:20PM0.33m
9:04AM0.66m
8:49PM0.30m
10:11AM0.66m
10:26PM0.30m
11:13AM0.68m
11:39PM0.32m
12:07PM0.70m
00:35AM0.36m
12:53PM0.72m
1:20AM0.41m
Low Tide
00:20AM0.09m
2:40PM0.26m
1:04AM0.12m
4:27PM0.26m
2:00AM0.14m
6:00PM0.23m
3:09AM0.15m
6:47PM0.20m
4:22AM0.15m
7:19PM0.17m
5:28AM0.14m
7:45PM0.14m
thunderstorm
thunderstorm
clear
clear
part cloud
part cloud
thunderstorm
thunderstorm
clear
part cloud
clear
part cloud
part cloud
part cloud
clear
clear
clear
clear
clear
part cloud
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
6:13
6:13
6:13
6:13
6:13
6:13
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
6:29
6:28
6:27
6:25
6:24
6:23
6:22
 mm
2
1
6
3
Temp °C
28
27
28
29
26
28
28
27
28
29
27
28
28
26
28
29
26
28
29
27
Feels °C
32
31
30
30
27
33
32
30
31
31
29
31
31
27
30
31
27
31
31
29
  • Map Icons:
  • Break
  • Live Wave Height (m)
  • Live Wind Speed (km/h)
  • Surf Rating (10 Max)
  • Ocean Swells (m)
  • Wind Speed (km/h)
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Information about the Grandma's Surf forecast

The above surf forecast table for Grandma's provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Grandma's can be found by selecting the local surf guide option on the grey menu. Our Grandma's 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 (Grandma's) 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 Grandma's 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 Maui? If you are looking for accommodation near Grandma's, camping, hotels and condos and appartments in Maui, consider staying in Kihei which is 10 km (6 miles) away. Other places in and around Maui where you can find information about places to rent, and car hire include Wailuku which is 12 km (7 miles) away, Kahului, Lanai - Lanai and Kaunakakai - Molokai.

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