It's in fish, so I can't use it myself (zsh), but I like this idea because where I live it's hot right up until about 45 minutes to sunset and everyone, including my family, goes out for a walk right at that "cool time of the day". I'm going to write a similar one for myself that I can use to find out when "walk time" is, thanks for the idea.
Sure, I can try, but it's definitely going to be a hacky, one-trick-pony script for my personal use, haha. I was more saying I would "rewrite" the idea of your script (it's very nice code, btw) into something for my walk time management.