OP, you say "free, open source, and fully attributed", but it's really not fully attributed. I know Google will live, but you need to be more attentive to licensure and credit. Here are some major problems (in no particular order):

• The weather icon pack is licensed under CC BY 4.0, yet you never mention this license. It's not sharealike ("SA"), so you can relicense, but it would be nice for users to know that you are, in fact, allowed to do that.
• You never link to the weather icons page so users can easily find the original icons.
• You say "inspired by Google's Weather Icons v4" but then never say what you changed or how. Did you modify them? Build these from scratch using Google's as a reference? You don't have to say for the license; this would just be nice. If it can't be summed up in a sentence or two, then fair enough.
• In "Credits & Acknowledgments", you never mention the Google Weather icons – which are the entire reason this repo exists. Given the only requirement of CC BY is proper attribution, something needs to go here.
• You don't even link back to the third-party repo where you got them from.
• Under "License & Legal Notice" and in your LICENSE file, you call the copyright status of the icons "uncertain". This confuses the hell out of me, because on the icons pack page for Google, it clearly reads at the bottom: Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License.
  • This to me indicates you did minimal research and didn't actually care about the license but called it "open-source" anyway and happened to get lucky. It seems like instead of finding the official source, you got them from this repo which is similarly sloppy.
  • One of the lines reads "No official Google documentation has been located that confirms these specific icons are released under an open source license". OP, for the love of actual god, this would've taken less time to find than it took you to type that sentence; below is the second result on DuckDuckGo for "google weather icons pack" after your own repository:

Now you have all your research done for you, and Cunningham's law is proven right again.