rw950431 on Trying to parse weather data with ThingHTTP but keep getting "Error parsing document"

Interestingly when I try your URL without any parse string I get the answer "-1" instead of the web page. Maybe wunderground is blocking thingspeak for some reason.

Is it an option for you to sign up for a free wunderground account and use the API? http://www.wunderground.com/weather/api/d/docs?MR=1