Boundaries with a partner that smokes a lot of weed

As some one with very minimal experience with drugs of any kind, I’m newly dating someone who smokes a lot of weed. His smoking habits were a big problem in his marriage (which ended about a year ago) and I’m trying to figure out how I feel about this issue.

I have no desire to monitor how much/how often my partner does this stuff. But I do feel like I need to know what headspace they are in sometimes. Like, if I want to have a serious talk or need to have help with something.

So question for people in relationships where one or both of you smoke weed…how do you make sure you are having the important talks at a time when you are both sober and in the right mindset for such a conversation?