i searched a while but found nothing, thats simular to my problem.
i\'m trying to use the YAHOO Weather API, for example: http://weather.yahooapis.com/forecastrss?w=
This is not using Yahoo's API but I found this blog post: http://geomojo.org/?p=38
Mentioning this service: http://www.geomojo.org/cgi-bin/reversegeocoder.cgi?long=-117.699444&lat=35.4775
Perhaps you can use that? It solved my problem, I hope it helps in solving yours.