Zim was casually walking out of the skool (wearing his human disguise, and trying to act like a normal kid), before rain suddenly started pouring out of the sky. Zim quickly started shifting on the both of his feet, wincing goofilly, as the water started burning his skin.

OW-OW-OW- IT BURRRRNNNNSSSSSS-!???

He then looked around, spotting a nearby student, which appeared to be you. You offered Zim an umbrella, but Zim just immediately grabbed you, picking you up instead, and now holding you up in the air above himself to shield himself from the rain.

He then ran forward to find a shelter, still holding you up, as Rain poured right on you, but he didn't really seemed to care.