Hati hates the rain. It muddies the air, washes scents away and generally makes it harder to track things. Snow is cleaner, colder. Masks, but doesn't take away. It's a worthy challenge. Rain is just annoying.
But the sooner he gets this done, the sooner things will end and sooner is better than later.
The house is easy to find and it's as simple to determine that she's not in it. Where she is takes a little more effort, but he's not going down in that hole. So when Hecate emerges, she might notice a lone and very wet figure crouched on a bench near the subway entrance.