After hearing some of Cait's random dialogue regarding weather, I wondered why she doesn't like it when it starts to precipitate.

When it was sunny, she commented that it was good she didn't have to go tramping through the Commonwealth in the rain.

When it was raining, she complained about getting soaked.

Why doesn't she like it when it rains?

Obligatory bad pun:

Why is she being such a wet blanket?

And just after I noticed this, Curie mentioned finding some meteorologists because she wanted to know if it would rain (she'd prefer it not to!).

It's often random. She would complain about how she can't wait to get out of "this goddamned heat" as well.

I guess it's just a personality quirk. I'm glad the companions have them.

I thought it was a general companion thing. Codsworth and Garvey don't like the rain either.

Really, who likes walking in the rain while carrying a ton of guns, ammo and armor? As for the robots dislike of rain, one word....Rust.

To be fair Cait doesn't seem to like anything, I'm having a hard time as she dislikes too much of what I do, I've ditched her for now and sent her to Sanctuary.

Three words, Curie is Synth.
So if she doesn't rust anymore, why would she care if it rains?