Keep electronic PCBs out of non temp controlled. Most normal parts are fine including coils. Keep sensitive equipment out of non temp controlled. If you have a lot of humidity, you are going to remedy that with a dehumidifier.

Some common sense applies here.

For clarification.

I have spare pinball parts in plastic bags in storage boxes in my garages all over the world for over 25 years. There are no issues. I just don't keep PCBS, ICs, or backglasses in non-climate controlled storage.

Some more helpful details.

The plastic bags I mentioned is how to avoid moisture problems unless your area is moisture saturated.
As the moisture can be trapped in the ziplock bags.

If you have excessive moisture in your storage area, blank playfields WILL warp over the long term.
They need to be stored properly, in their boxes preferably, sealed, or at least upright.

However, you can make a simple sealed "storage closet" and use a room humidifiers/dehumidifier with no issues.
All you have to use is 2X4s, plywood, and edge sealant.
Amazing what you can do with simple building materials.
If you have a LOT of playfields (NOS, used, repo, etc), you may want to consider this option.
I have friends with stacks of used playfields in their shop under those conditions.
Right now I have a number of repo playfields "in the open air" letting the clear coat further cure for the next few months before I box them up again.

Game playfields will "plank" under the same circumstances, but can be remedied by using a things like a guitar case humidifier in the cabinet. However, this also is dependent on how they are handled during maintenance. Using factory cheater bars will cause negative torque twisting which can cause the cracking, along with the type of playfield coating used for protection.

I really don't know how severe your specific are in WV is overall, Vid offered some research.

I had games in storage "vaults" for over a decade (Many in individual crates), and when they came out of storage, they were almost untouched. Granted all needed technical inspection and servicing, mostly on simple things like switches, diodes, ICs and power voltages because nothing had been operated. No pinball machine does well indefinitely, if they never get played, although EMs operate the best when the are played regularly. SS games need the "love" too.

The one thing that will happen regardless if the games are perfectly climate controlled or not is the "white corrosion" oxidation which occurs on galvanized steel.
The older the game gets, the more it happens.
This is not "dangerous" except for electronics, optos, and PCBs.
The metal can be cleaned and polished.