Good question. I'm in the same boat here. I noticed earlier that around 9:30am, it stopped giving updated weather. Then about an hour ago, I started getting the error you're receiving. Here's hoping it's temporary.
It's been a couple of days since my application shows an error that cannot find the "temp" node on the XML. Today I decided to debug it and apparently, it is the API's fault. I tried the Yahoo Weather app on my iPhone and it says that weather data cannot be retrieved. I hope this is just temporary, and that Yahoo is looking into the problem!