Plain English Meaning
SS in a weather report tells you that strong winds are blowing sand around at the airport, badly reducing how far you can see.
Full Definition
In a METAR, SS is the weather code reported for a sandstorm — strong, sustained winds carrying large quantities of sand particles through the air, reducing surface visibility, typically to less than 5/8 statute mile.
Context Anchor
You will see SS in the present weather part of an airport weather report, especially for dry, sandy regions with strong surface winds.
Why Pilots Care
Sandstorms cut visibility sharply and can damage engines or sandblast surfaces, often forcing delays or route changes.