Boreas is a simple weather forecast front-end, powered by the NOAA National Weather Service. It uses data from the US Census Bureau to translate an address into a longitude and latitude, and then pulls a forecast for that location. Because it relies on US government datasets, it only works in the US.
To use Boreas go to the Forecast page and input your address (or a nearby address) and click "Submit" to see the current forecast. Boreas displays a 7 day forecast with each day broken into day and night sections (14 sections total). You can click on a section to see the hourly forecast for that particular section.
Once you have submitted an address it will be added as a parameter to the URL, so you can bookmark that URL to return to later and save yourself having to input your address again
Boreas is implemented as a Ruby on Rails application. You can check it out on GitHub. It is MIT licensed, and you are welcome to run your instance if you like.
You can find information about the NOAA National Weather Service API here
You can find information about the US Census Bureau Geocoding API here