I feel like the lamest broken record when I get this question, because I don’t remember. I started writing SLA when I was a preteen, and because of that, I don’t remember where I got the initial ideas. All I do know is I wanted to write a book where winter was perceived as the “good guys.”
As for the rest of the world: when I rewrote SLA a few years ago, I knew I wanted to keep the Season Kingdoms, but I wanted a balance to it, some “normal” kingdoms — thus, the Rhythms were born (and were named as such because they cycle through the normal “rhythms” of nature, i.e. four distinct seasons).
Thank you! I’m so glad you liked SLA :D