Well part of the reason that happens, is because it's based on actual whether network info. And honestly, most countires weather service doesn't cover smaller cities.
For instance, I'm in Waco, TX (which tracked). But the next major tracked city is Waxahachie I believe and then Dallas. Each of these are 30 minutes apart northward.
It would be nigh impossible to have near exact weather conditions for every single city posted on the weather channel I would think.