Yes, this was brought to our attention just a couple days ago. There are some options we are exploring here: there is https://openweathermap.org/ and also https://console.bluemix.net/catalog/services/weather-company-data
It sucks that wunderground suddenly closed their free API keys, and has done it in such a brutal way. Existing keys that have already been created still work at the moment. We will have to change the API to one of the above soon.