The earth weather app shows you the current weather and a 4 day forecast for your current location. If you want to keep track of the weather in different locations at once you can add these cities too. They will always show up as a different tile under the weather information for your current location.
For an better overview with multiple locations it is possible to give each location a different background color, the button for this function can be found in the detail/forecast view after clicking on the location tile. Also a share button is available in each location tile to allow you to share the current weather and forecast with your friends and family.