It picked my location perfectly, but then gave me a temperature in Fahrenheit. All you need now is to match locations to measurement standards (ie. US, UK and that one other country imperial, all others metric).
I was raised in the UK, and used celsius. Now I live in the US and have learned to use Fahrenheit.
On a related note, I was very annoyed that Yahoo Weather will allow you to either choose centigrade and kilometers per hour, or Fahrenheit and MPH, but not to mix and match. Insane.
Probably best to show both.
The answer to "is it going to rain?" here is always "Who knows? Probably... can't really say. It looks sunny outside, but it was raining this morning so it might rain again later today."
You've earned a little spot on my bookmarks toolbar.
With unicode domain names, you could have preticipation?.com, although it may look a mess in non-Firefox browsers.
AFAIK the UK uses celsius mostly.