I finally found a decent replacement for Dark Sky now that the Android app is dead: Geometric Weather. I recommend it because it's FOSS.
I pick my apps based solely on whether they respect privacy, and I couldn't seem to find a privacy policy for this one. So, here is the Exodus report for it.
It is also worth pointing out that this app is Chinese. Whether or not this would make a difference in how privacy-friendly this app is, I don't know. Call me a lib, but this is still something have anxieties about.
Geometric Weather is not fully-free as it contains binaries with unknown (probably non-free) license. https://github.com/WangDaYeeeeee/GeometricWeather/issues/9
Pro tip: whenever you see an app on GitHub that isn't on F-Droid, just search for "F-Droid" in the issue tracker and there is more often than not something blocking it.
I use "Your local weather," it works reasonably well for my purpose.
Thanks for pointing this out.