Acid Rain (Natural Event)

Acid Rain is an event that has a 10% chance to occur instead of normal rain. Acid Rain will inflict Poison if outside, as well as destroy some blocks. It can only occur once a shadow orb is destroyed in that world and atleast 3 NPCs are vacant in a room made of anything but corrodable substances (see Main heading)

Main
Acid Rain is basically a much more gray variation of rain. It can corrode some substances:
 * Wood
 * Cactus
 * Pumpkin
 * Stone
 * Iron
 * Copper
 * Tin
 * Lead

Warnings
Acid rain starts a little later than the event itself. Here are some tips to indicate that an acid rain event is about to occur:
 * 1) If the sky starts to turn completely gray with a gray haze in the screen: Warning 1
 * 2) Acidic sounds are heard: Warning 2
 * 3) The background shows gray rain: Warning 3
 * 4) Blocks start to break due to corrosion: Warning 4
 * 5) The acid rain begins

Precursors
The day before an acid rain, the sky will appear darker and smoggier than usual. The clouds will be very dark.