You can't. You don't want weather updates? It doesn't continually run in the background only when it updates the weather. How much battery is the app consuming? Not every app that runs in the background uses a lot of battery resources. Some do, but not weather.
Go to settings/apps/weather. Scroll down to the battery section and you and it will say x% used since last fully charged. If it's less than 1% leave it alone, it's not using any battery. If it says 0%, it's certainly not using any battery. Also, if you do not have the weather widget on your screen, it will not run in the background, it will only update your weather when you open the app.
Why do need it not to update? If your intent is to save battery, it's not going to save very much. You can check your battery usage to see gow little it uses. If you do not want it to regularly update, do not keep the live widget on your screen. The weather will only update when you open the app. You can also go to the weather app settings and turn off auto refresh. It's still not going to make any significant battery savings.
