Currently the program has very simplistic error handling which makes sure the system is left in an 'on' state and goes back to sleep if any error occurs. 

I am suspicious that the Wunderground API might be the source of some errors and have written a Python test program on my Raspberry Pi to call the API and record any errors that occur. Results from this can then be used to improve error handling, perhaps by querying an alternate PWS if the primary returns an error.