Well, does your concertina ever get a cold? ( We get them a lot in UK)..But taking joke aside; atmosphere can affect reeds, as they are a metal after all. Metal may buzz more, or tighten up here an there!
I have been lucky in having minimum problems on my concertina generally over the years, a few buzzes, maybe, and it goes in its special padded box, protected from atmosphere!
Have you all had any problems with say damp weather, or dry weather, affecting tone quality? Be interesting to compare notes!