Temperature range for brumation

[Invictus]

With the brumation season just around the corner, I've been thinking about how I'm going to go abotu brumating my snakes this year. I'd like to keep them in my house, but the best I can do as far as low temps go is 68 degrees in my basement, which is fully finished. What I want to know is, has anyone ever brumated at around this temp? Is it safe, or is that just cool enough to kill them, but not cool enough to slow down their metabolic processes? Will it be effective enough for milk snakes and king snakes?