I see no Json at the given URL. Where do you plan to use it?

I don't want to. I was premature in posting that...I think.  The wunderground API only has documentation for Json, but it seems like XML is still possible.

Looks like it is either XML or Json, depending on the suffix you add to the URL. So no need to mix the two modes.

I think you're right.

Indeed.
You have to navigate the XML data in depth (the hierarchy, the children) and in width (the siblings).
Without XPath, it is difficult...

Moreover, you use getString(), which is used to get attributes, but this XML has no attributes. You must use only getContent().

1. XMLElement xmlFeed = new XMLElement(this, "http://api.wunderground.com/weatherstation/WXCurrentObXML.asp?ID=KILCHICA30");                                             
2. int numSites = xmlFeed.getChildCount();     
3. println(numSites);
4. for (int i = 0; i < numSites; i++) {   
5.   XMLElement tag = xmlFeed.getChild(i);
6. //  println("#" + i + " -- " + current_observation);
7. //  XMLElement[] kids = current_observation.getChildren();
8. //  for (int k = 0; k < kids.length; k++) {
9. //    println(kids[k]);
10. //  }
11.   if (tag.getName().equals("temp_f")) {
12.     String temp_f = tag.getContent();
13.     println("temp_f: " + temp_f);
14.   } else if (tag.getName().equals("temp_c")) {
15.     String temp_c = tag.getContent();
16.     println("temp_c: " + temp_c);
17.   } else if (tag.getName().equals("relative_humidity")) {
18.     String relative_humidity = tag.getContent();
19.     println("relative_humidity: " + relative_humidity);
20.   }
21. }
22. exit();

Wow, thank you.  Why does the URL you used work?  Your totally doing this w/o their API, right?