Earlier I posted that temps over 100* would harm the kefir grains, but I'm coming back to edit this because I'm betting some of the lactic acid bacteria would survive. While it would ruin the grains you could probably end up a yogurt starter that contains a few of the original strains.
Let me know if you try this and how it turns out. It would probably be all the same to use a tablespoon of kefir rather than the grains to inoculate the milk.
Post Edited (Buren23) : 4/14/2012 6:23:06 PM (GMT-6)