If at all possible bring them inside. Its the BEST option. If its not feasible then don't sweat it. Keep them dry. Extreme temperature swings are the problem. Don't power them on until warmed up for 24 hours. Condensation is the enemy. And you get lots of it when you turn on a machine if cold. Electronics don't like it and neither does your backglass, playfield or cabinet.

Most games we have played have been stored in non-temperature controlled environments. That 8k AF. The $75 EM. And the newest JJ/Stern. If it was kept dry, they pulled the machine out of storage, let it warm up and did the norm before selling it to you and everyone else.

Also while we are on the topic, most games prior to 2000 probably saw the back of a pickup truck, lift gate or trailer while it was raining. FACT.

We baby the shit out of these machines like they were meant for our living rooms. New Sterns are getting closer to that reality.