Toward Ecosophy

It's not that the Rites make you more susceptible to cold, it's that the specific things the Rites are meant to do for you are disrupted by cold, so it's not useful to combine the Rites with cold exposures. All that means is that you'll want to do some other kind of exercise. As for this exercise, Gardener's book doesn't specify, and I know of no reason why this would conflict with cold exposures -- it's not meant to work with the seven etheric vortices, it's specifically aimed at the cerebrospinal fluid.