iOS 7 weather app shows wrong sunrise/sunset time
The clear error would be a city in another state or country.

The sunrise and sunset data for Minneapolis, KS is going to be different than Minneapolis, MN.

Once you have ruled that out, you might need to file a bug with Apple in the case that their app is either requesting the wrong data from the weather service provider or the data source needs to be corrected. In both cases, you can't really change what happens in code or upstream and could only try to find a location that's close enough for weather purposes that has correct (or close enough) sunrise and sunset data.

http://apple.com/feedback might also be workable rather than filing a bug if enough people have issues where the current data set is lacking or off by hours.