Sandstorm

Sandstorms are large clouds of dust generated by strong winds blowing in a desert or wasteland.

In Advance Wars: Dual Strike

With the exception of Max's Artilleries (due to them only having a very short range anyway), all indirect-combat units lost 1 space of firing range. COs with the Sand Scorpion skill rank got a 20% attack boost in sandstorms.

In Advance Wars: Days of Ruin

All units not controlled by Penny lost 30% attack power, but indirect firing range was unaffected.