You'll need to trade for it or wait for another event for Pokemon Thundurus, because you can't get Thundurus in Pokemon Black.
Thundurus is version exclusive to Pokemon White, you'll have to trade.
Do you mean Thundurus? Thundurus cannot be in the wild in Pokemon Black, but you can trade for it or wait a Mystery Gift Event.
You can't find thundurus in the wild in black. You need to trade one over from white version or GTS.
Trade from white and if you have white trade from black for tornadous
You cannot get Thundurus in Pokémon Black, the only way to get it in Pokémon Black is by arranging a trade with someone else in order to get Thundurus. Thundurus is a Pokémon that is exclusive to Pokémon White however its counterpart, Tornadus is available in Pokémon Black.
I'm sorry, but u can only find him in Pokemon White. I think Tornadus is in pokemon Black though.
Pokemon Black- Trade from White. Pokemon White- Thundurus roams Unova. After getting 8 badges, go to route 10, go into a house, leave, meet Thundurus and he'll fly off and start roaming Unova.
you find Thundurus at route 7 and then it starts roaming the Unova region. Hint: you can find out what route Thundurus is on by watching the bulletin board when you go in a green building. It is level 40 when you encounter it and once you move or do something like give your Pokemon a potion it runs away (The wild Thundurus has fled).
After hearing about a storm in Opelucid City fly there and go by the house where you can heal your Pokemon the women who lives there will tell you to come inside after hearing the story about thundurus go back outside where you will see thundurus it then flys away you can find him. When major storms occur in the region but he will flee from battle thundurus is only in white.
Thundurus is only available in pokemon white. It needs to be traded from white into black. Tornadus is like thundurus, but it looks different and is a different type. You can only find tornadus in black version. With both in your party, you can go to the abundant shrine to find the legendary pokemon landorus. Landorus is available in bothe versions. He is level 70 so come prepared. When looking for thundurus/tornadus look at the sign that says the date when going through the small buildings that separate some towns and cities from routes. It will say thunderstorm/wind storm on a certain route. Don't fly to the nearest town, because it will move positions. You will need to try your best to find and catch thundurus or tornadus.
On route 7 is where you first see it. Keep going down the route until you find a small cabin, where an old woman will tell you a story. After you walk outside, you will see Thundurus. -EDIT By the person who provided first answer- You must have beaten the Pokemon league first.
Tornadus isn't in Pokemon white, so you have to trade from Pokemon black... if you get Thundurus and tornadus, go to the abundant shrine and the third one will be there. i cant remember his name though...