On an acoustic especially it can make a difference. As the humidity drops the woods dry
out and shrink slightly. The net result of this is that the top of the guitar goes a
little flatter and the action lowers.
However, we are talking fractions here.
So for the majority of players it really doesn't make a material difference. But if you
absolutely INSIST on the lowest possible action then your tame tech will be able to take
that into account. And if you really do want the lowest possible action and your guitar is
sensitive to changes in humidity, it is worth getting two saddles made. A high one for dry
conditions and a fractionally lower one for more humid weather.
But with that
caveat, it really doesn't make a great deal of difference.
When the going gets weird, the Weird turn Pro.