My voice always does weird things in the winter, I think it's partially because the heat where I live is very dry (forced air). My range seems to diminish from late November until the end of February.
I need it more than ever, I used to be pretty much strictly a backing vocalist, but over the last few years I've been doing more leads.
I've got a friend who fronts a really good Southern Rock tribute band in Vegas, we used to be in rival bands here. New Orleans must be fun to play too...