The app now supports watchOS 4 and can potentially have a complication, however in testing the complications have a very small CPU and network budget, so it can only update a few times per hour, then it gets stuck on the last update. This makes it show the wrong prediction for a while. I’m looking into ways around it to reduce the CPU and network, but it is a fundamental issue with the way complications work in watchOS.Mili commented
I can add rain parrot to my complications on my iPhone app. But when I update my watch face rain parrot does not appear in the drop down menu. This is no good as I purchased the app so it would appear in my top left complications not in my apps.