Doesn't seem like a "temporary" issue as I've been getting error alerts every hour starting at 4:39 AM PST. So it's been down for at least 9 hours. Also, just going to http://weather.yahooapis.com/ gives a 404 as well, which concerns me a bit more...
Hey, just so you guys know... I wrote Yahoo and got a response saying that they are aware of the issue and are working on it. I'll post here when I get more information.
I still have a problem with this service not working from certain networks. The URL http://weather.yahooapis.com/forecastrss returns the Yahoo 404 page for some of my servers in the USA running some code I used to consume the RSS feed yet the same URL hit from Australia and other servers in the US work fine. When I initially developed the application making use of the feed the URL was http://xml.weather.yahoo.com/forecastrss, strangely this is working from all my sites but considering it isn't documented anywhere anymore I don't want to leave my configuration with that.