Sandstorm

A Sandstorm is a Desert event, and when it fires it fires in every Desert in the world at once. Sand streams sideways across the screen, sight lines shorten, and the wind pushes your character around constantly through the Mighty Wind debuff. The particles take their color from whichever Desert you are standing in, so a Corrupt, Crimson or Hallowed one looks different from a clean one. On Color or White lighting the effect is heavy enough to cost frames on a weak machine, and the Retro or Trippy settings strip most of it away.

Sandstorms hang off the wind speed. Nothing can start until the wind is above 30 mph, and once it is, the game rolls every tick. In practice that averages out to about 12 and a half minutes of sustained high wind before one begins, or closer to 8 and a half in Hardmode where the odds are half again as good. A storm that does start runs somewhere between 8 and 24 minutes, decided the moment it begins.

The wind ends it too. If the speed drops back under 30 mph, whatever time was left is divided by 15, so a storm with a quarter of an hour to go is finished inside a minute. There is no way to summon one and no status message at either end, which leaves a Weather Radio or a look at the Desert as the only ways to know one is happening.

Mighty Wind shoves you in the direction the wind is blowing, harder the faster it goes and harder again while you are in the air. It deals no damage. What it takes is control, and in a Desert full of open shafts down to the Underground Desert, that is what kills people. Cover the entrances along your route with platforms before you plan to fight there.

• Walking or running into the wind cuts the push, so keep moving rather than standing still to shoot.
• Background walls cancel the debuff. One row of wall along a path you use often makes that path behave normally.
• Any grappling hook holds you in place, so hook the ground or a tree when you need to stop.
• Dunerider Boots and everything built from them, up through Lightning Boots and Terraspark Boots, give you enough speed to work against it. Roller skates suppress it outright while you roll, coast or stand.
• Fast mounts ignore it while they are moving, but the push returns the instant you stop.

Sandstorm enemies need real sand under them. The game looks for at least 40 connected sand blocks of any variant inside a 9 by 9 area with the candidate tile at the top center, which is why nothing spawns on a thin sand veneer and why paving an arena shuts the spawns off completely. Remix and Zenith worlds cut that requirement to 10 blocks, so storms there are far busier.

The roster is the reason to turn up. Angry Tumblers roll along the ground and want a sidestep rather than a block. Underground Desert regulars including Sand Poachers, Tomb Crawlers and the mummies come up to the surface where you can actually reach them. In Hardmode the Sand Elemental appears, and it is the only source of Forbidden Fragments and the Spirit Flame, which turns a Hardmode Sandstorm from a nuisance into a farming trip. Sand Sharks and Dune Splicers swim through the ground and will reach you on a raised platform, so height alone is not safety.

The whole event lives on the Desert surface. Fly over the biome or drop below the surface layer and none of it applies: no debuff, no spawns, no visibility loss. If you have business in a Desert and no reason to fight, that is the entire answer.