The app can also integrate into GNOME Shell: you can see the weather of the last unknown cities (the city name is entered in browse mode).
To search and add new cities/areas you need to click on the New button, enter a search name in the search bar, select from the dropdown list the desired location and press Enter.
Installation latest version into Linux Mint:
The Weather app is in the repository system by default, which means that it helps to open the Software Manager, type in the search box the word Weather and press the Install button.
Or run command in terminal to install:
sudo apt-get install gnome-weather