Found Surface Rust On/Around My Battery Tray
 

My car has been parked outside and after a recent storm, I took out the trunk carpet in preparation for cleaning and found water and light rust around the batter tray? However, I couldn't source the leak?

This happened during an extreme cold spell, so I'm guessing that ice had formed along the rear trunk lid and dripped onto the carpet/spare tire well/battery tray. But, as I mentioned, I couldn't pinpoint the actual source of entry.

BTW, CHECK YOUR SPARE TIRE PRESSURE! Mine was at zero.

probably battery leaking or spilled

This. Unless you're running an AGM battery.
If it is an acid battery, where is the vent tube running?

Hhhmmm, never thought of this (leaking battery). However, it is an Interstate battery, sans vent tube. I thought the issue might be a clogged rain/drain tube.

Mods, please delete (double post)