With Dark Sky shutting down their API, this has been replaced by a Pirate Weather workflow.
Download and install the the latest pirate-weather.alfred-workflow
release. Obtain a Pirate Weather API
key and set PIRATE_WEATHER_API_KEY in the
workflow environment variables.
You can still use Dark Sky as a data source until the API is actually turned
off by setting the PIRATE_WEATHER_ENDPOINT environment variable to
api.darksky.net.