One app I often use before deciding to take flight is UAV Forecast.
This is a very handy app that can help you decide to fly your drone or not.
The app is pretty basic, and shows all you need to know in 1 screen.
Adjustments can be made to suit your needs for flying, but the default settings are pretty good for most pilots.
Of course peeking outside gives the best view on the weather, peeking outside does not tell you anything about satellite visibility and KP index.
Especially KP index is very important when you are flying with GPS on.
The higher the KP index, the more interference you’ll have on GPS, this could cause all sorts of issues like toilet bowling and even worse.. flyaways.
Here are some screenshots from an Android device
This app is currently unavailable for Windows Phone users, but they can add a shortcut to their home screen and use the website instead.