That is certainly not ideal.
At the very least, I would be sure to throw a few dessicant packs in there before sealing them up.
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If we are talking about big $ speakers, or several speakers that add up to big $, then I would suggest 2 other options.
Sell them now, and replace them later to avoid the risk of damage during storage.
Or, look into a small climate controlled storage rental.
Perhaps my personal experience would provide some guidance. I bought a set of the Mackie CR3 for dedicated garage duty, and I got ~5 years of service life in my garage (Central Tx, very high heat and high humidity). Seems to perhaps be a problem with the volume knob, which is to say more of an electrical problem vs. a speaker problem.