Technically, wouldn’t you need the guy 10 minutes in the direction of the rain cloud to have turned it on when you go on a hike? Makes the battery saving argument kinda moot I guess, you should get the notification anyway, if enough people in your area are providing sufficient data for the short term forecast.
Now in order to make that happen, people should participate if they’re using the feature, but that’s almost a moral argument I guess.
Anyway, would still be nice if iOS / Android had more fine grained permission controls.