[Finally, something that she knows the answer to... Illness nods once, speaking in as authoritative of a tone as she can,]

... Layers!

[Wait, that doesn't make sense by itself...]

Uh, you need to put a lot of clothes on. First a shirt, then a sweater, and a couple jackets never hurt either... Then you just crawl inside of the nearest box or alley and curl up in a corner annnnd hope you don't freeze to death.

[There's a faint twitch that might be a smile and a beat before she adds, as an afterthought,]

You'll freeze faster if you're wet.