After following the secret path through the fog in the Northwestern Sea, you can sail to the Isle of Gust.
To the Isle of Gust
If you went through the correct route, the fog will disappear and you can sail to the Isle of Gust.
After you land on the island, go north and there will be an area of Miniblins. The wind will blow from the east, so be careful not to be pushed off of the left side.
Make your way east. Wait for the wind to stop before you try to jump across gaps. When you reach the east side, go north, then go down to the lower area on the left. Kill the Miniblins, and go to the left. Wait for the wind to stop, then take a bomb flower and throw it at the crack in the wall to the north. When the bomb opens the cave, go in.
Open the chest, then read the journal. Check the map to the right of the desk, and copy the Xs and arrow on your sea chart.
Go outside, and go east and up the stairs. Stand on the area below the sign, and run to the left when the wind blows. The wind will push you far enough to jump across the gap. Jump over the next gap the same way, then go down the stairs to the area below. Kill the Miniblins, then go west. The stairs will take you back to the ship, so go north and enter the cave.
Go east. There is an area down below with Miniblins and a treasure chest. Open the chest to get a Wisdom Gem. If you kill all of the miniblins, another chest appears. It contains a treasure map.
Go southeast to leave the cave. Then go east, kill the chuchus, and stand on the air vent to the right to be pushed up to the ledge above. At the top, wait for the wind to blow from the right and run left to let the wind push you to the ledge on the left. Go west from there and go down the stairs to an area with stone tiles. Go north and you will find the temple, but the wind won't stop blowing. The stone tablet gives you a clue about windmills. Look at the map to the right of the stone tablet and copy the X onto your map.
Go south, then southwest, and stand on the air vent to go up. Then go north to the next area.
Go west, then south to the next area. Go down to the lower area and Ciela will mention the sand piles on the ground. Go southwest and dig up the pile of sand that is below the ledge on the west side of the area. Go up the air vent to find a chest that contains a Power Gem.
Jump down to the lower area, then go east and dig up the sand below the ledge there. Float up and go north to the next area.
Dig up the sand on the left side and float up, then go north. There is an air vent blocking the path, so use the shovel on it to cover it up. Go west and float up the next air vent. From there, go northwest and dig up the small X in the sand to get a big green rupee.
Then go east and float up the air vent to find a stone tablet and a map. The tablet says that you need to blow on the three sacred windmills, and the map shows you where the windmills are. Make a note of their locations, then go south to jump down the ledge. Use the shovel to cover up the air vents that block the path to the east, then go east.
The statue up above warns you about monsters up ahead that are sensitive to sound. Walk slowly east onto the sand. There will be some stairs up to a ledge above you, with two bomb flowers and a statue. It says that the creatures will eat whatever they find, so throw a bomb onto the sand. The sandworm will eat it and explode.
With one sandworm gone, you can safely go to the northeast, where there is another ledge with bombs. Go up and get a bomb and throw it down onto the sand to destroy another sandworm.
Go southwest from there and go past the bomb flower, then go up the stairs to avoid the sandworm in this area. Then go get the bomb flower, throw it on the sand, and go up the stairs.
Then go southeast. There will be another sandworm in this area. Go up to the windmill that you marked on your map, and blow into the microphone until the windmill starts spinning permanently.
There is a chest south of that windmill that contains a treasure map. Go northwest from there, then west to the northwest windmill. Blow on it, then go south to the final windmill and blow on it. A couple of doors will open, and the wind around the temple will stop blowing, allowing you to enter the Temple of Wind.