Since openweathermap.org recently changed the API, it’s now neccesary that every user of the pimatic openweather plugin needs an individual api key!
The procedure is relative simple. Update to the latest version of the openweather plugin, then go to www.openweathermap.org, create an account (for free) and copy the API key shown at the “My Home” screen to your plugin as follows :
{
"plugin": "openweather",
"apiKey": "xxxxxxxxxxxxx"
},
That’s it! Now enjoy the openweather plugin again!
For more information have a look here : https://github.com/josecastroleon/pimatic-openweather/blob/master/README.md
(thx @mwittig for clarification 
)
