Rain is a weather condition in Advance Wars. In Advance Wars 1 and Advance Wars 2: Black Hole Rising, Land vehicle units not under either the command of Drake or Sturm, or the influence of one of Lash's CO Powers, are affected by movement in rain with an increase of 1 in Movement Cost on Plains and Woods. Olaf will have his units all affected as if the weather was Snow instead.
When Fog of War is in effect, rain will decrease the vision range of all units by 1 in all games except for Advance Wars: Days of Ruin where the vision range of all units is reduced to 1 and the vision range of all Buildings is reduced to zero. In Advance Wars: Dual Strike and Advance Wars: Days of Ruin, if disabled, Fog of War is immediately in effect when it rains.
- In a game where Drake is present and the weather is random, the chance of rain appearing is increased by 7%.
- In Advance Wars: Days of Ruin, units under the command of Penny have normal vision range in Rain, even if those units are not in her CO Zone or even if she has not boarded a unit.