Wthr is a simple Firefox OS app. It uses HTML5 geolocation to get the device current location, queries World Weather Online APIs for weather informations and change the background color of the app accordingly (the color ranges from dark orange for a high temperature to dark blue for cold one), it also changes the weather icon (Climacons) based on the weather description.
Go to wthr.feras.us on your Firefox OS browser and the install dialog will appear.
The website is sunsited 🌆 for now, untill Firefox Phone takes over the world, bye bye Firefox OS.