Realtime weather information provided by OpenWeatherMap
Webpage: http://openweathermap.org/
License: CC-BY-SA 2.0

The text below was grabbed from http://openweathermap.org/copyright

Terms and Conditions

All data are provided under the CC-BY-SA 2.0

All data can be used as an extra layer for any types of map. Since the is are no limits to use data please refer to a few simple rules to work with data.
Rules of working with data

    No registration is required before using the maps
    No API key is necessary. If you get < 1 rps
    When you use data from the website, please give a link to the openweathermap.org
    Commercial use is permitted and encouraged
    Data may be cached and/or redistributed, under the terms of the OpenStreetMap license CC-BY-SA 2.0
    If you need bulk downloading please contact to web-site developers by denn@OpenWeatherMap.org