Caching problem use jquery ajax to make a request

I'm using the JS API to get the JSON response. However, when I set "cache" to true, the call continues to append a random query string to the request and I'm getting "Cache-control:no-cache, must-revalidate, no-cache="Set-Cookie", private" in the response header. See my code below. Am I missing something here?

$.ajax({
url:'http://api.wunderground.com/api/723d8...'+ thisLocation +'.json',
cache: true,
dataType: "jsonp", ....

P.s. thisLocation is be declared in the top of the page, before this request is made.