Yup, I suspect that site is looking for local weather stations nearby and using the current conditions reported as a basis for a suggestion. That will be most accurate for current conditions.
With Coat I used projection data to give the whole day in a (hopefully) simple and concise single page.
Yup, sadly outside the United States, cost free weather data seems very rare. In my initial search I found many meteorology agencies (even those publicly funded) required payment or licensing for using the data.
For the UK, the service is Met Office and their licensing/pricing terms were enough to make me reconsider including that data in the first version.
Ok, I'll look into that too. The app only offers weather forecasts for the continental US so I originally assumed most folks were interested in fahrenheit, but I can see the appeal of celsius :).
It looks like those zip codes weren't in the original zipcode dataset. I'm adding them now, thanks for pointing that out!
update: It was actually a bug in the code, fixed now :)
I recently built a project (http://www.coatapp.com - A simple weather forecast application with clothing suggestions) on Linode and couldn't be happier. The disk speeds are very impressive, and super useful for apps that deal with large amounts of data that gets updated frequently (i.e. weather data).