Candidates should probably go into the application process with a version of a job talk ready (or at least a really good dissertation presentation that won't take too long to edit/fix for a job talk.) When you get your first phone interview, definitely prepare a talk (but perhaps without school-specific details or anything you couldn't use in a future year just yet).
I would definitely prepare a talk in your case. There is a very low chance you'll have a super fast request for an interview because at most schools classes are finishing this week or next week at the latest. Typically campus interviews aren't during finals because they want you to meet some students. So you probably have some time. But putting the calendar month aside, often when you're notified for a campus interview, it happens a week or two later. There's not a lot of time. If you're applying to a place that prioritizes teaching (even just a bit), you will likely need to do a teaching demo. THIS is what you want to prepare after the invite (not before because the guidelines are so variable). You don't want to be working on your research talk much between invite and interview.