How to make SandStorms?

Minecraft's weather is done through particles. You can create global logic variables for determining whether or not the "Sandstorm" is active.

Procedures will then need to be summoning the particles around the players, and will do whatever other effects you want to happen inside that procedure.

Particle spawning blocks you will need are:

Spawn [number] particles on server-side at x: [x] y: [y] z: [z] in area dx: [number] dy: [number] dz: [number] with speed: [number] type: [particle]