Well crap. We have a 2018 Buick Enclave Avenir and 2021 GMC AT4 pickup and I didn’t realize that they probably have that option already. Perhaps I should read my owner’s manuals!Our 2017 and 17 GM vehicles do have the headlights come on when raining. Indicator on the speedometer lights up too. Got caught in a heavy rainstorm in our '17 Terrain on the interstate just after we got it, couldn't see 10 feet ahead. Couldn't figure out how to turn on the headlights, or the 4 way flashers. Just about panic mode there. Soon as I got home I educated myself and the wife on this and I found out that the full headlights do come on with the wipers. And real surprised that the flashers were not on the steering column - like every other car ever built.