I've been playing around with it for a while, and these are my thoughts so far:
The placement of the hamburger menu to the right strikes me at somewhat counter-intuitive, and also goes against the Android HIG. I'd much prefer a regular App Bar.
The use of full-screen mode is also kind of annoying – in my opinion, this mode should be reserved for content that calls for immersion like reading a book or watching a movie (and the Android HIG says more or less the same thing). I don't spend that much time in the weather app, and having to hunt for my home buttom when I'm done is kind of a hustle. There should at least be an option to disable it.
Why would I need to know the temperature in both Celsius and Fahrenheit? Also, a back-slash is not the right character to separate two temperature values, which adds to the confusion and looks off from a typographic standpoint.
The dark theme is neat, although it would be nice to have some options. But the dark widget really sticks out on most home screens, as does the dark notification. Also, that circle around the weather icon in the widget and notification adds unnecessary clutter to something that is otherwise quite minimalist.
The photos are nice and all, but sometimes it's not entirely clear what kind of weather they denote. A weather icon next to the temperature info would be nice.
All in all, I like the general style of the app. It also seems to work well from a technical standpoint, e.g. finding my location and updating like it should. It's just that some things, like the full screen mode, strikes me as form over function. Where this to follow the Android HIG, I could see myself using this instead of Weather Timeline which is my current daily driver for weather info.