Humidity too high?
 

How would one keep humidity levels low while storing a guitar in a case? Currently its reading 58. I heard that the optimal levels are in the mid 40’s

A room air conditioner or dehumidifier is your best bet.

Where are you located? I seriously doubt that ~60% RH will cause you any problems for a short time. Most of our summer in New England is over 60 (June was almost entirely 70% or more). There is some risk of your guitar swelling with high humidity.

I guess I'm more inclined to worry about low humidity (in the winter around here), since I've cracked guitars badly before I knew about this issue. In the dry months, I am religious (now) about using a room humidifier and case humidifiers (baggies w/ sponges and dampits) as RH routinely gets down around 30% (or less).

I'm not sure if this is good advice or not, but I tend to down-tune my instruments a whole step or so while they're not being used (in case or on stand), particularly in the humid months. It seems reasonable to me that reduced strain on the bridge would help prevent the top from bellying or otherwise getting out of proper geometry. Maybe I'm kidding myself on that.