Many user are issue in Phone 7/8 plus, iOS 11.0.x, and the weather widget doesn't refresh at all, Changing regional settings does not help. Even launching the weather app from the widget doesn't even cause the widget to update. When we tap on it, just the widget portion of it doesn't update it's temperature. Similar issue with the weather widget on iPad, so clearly something has wrong in iOS 11 which is causing it to not work properly. Some users say that weather widget is refreshing sporadically or randomly. Below are some fixes that you should try to fix the "Weather widget update issue ios11" issue.
Fix 1: Make sure location service is set to ON
Unlike the iOS 10, now the weather widget only updates with location services always on. If this still does not work try deleting and re-installing the Weather app with location services always ON.
Fix 2: Wait for any changes to load
If you have done time changes in your iphone it may happen that after some time the weather widget fixes it itself, it just takes a few hours to catch up to the time change.
Fix 3: Update to latest iOS
It is very much likely that the issue is due to iOS 11 glitch, so keep updating to the latest version of iOS to make sure get Apple fix for the issue.