Heck I keep mine outside down to below freezing night temps, around the end of October, they have antifreeze running thru their veins 
Lately we have had temps like you highs 70 low 50 and my boxies have pretty well shut down feeding for the year, and they are doing a lot of pacing around looking for a place to brumate, confusing for them, they must be looking for my basement,lol cause thats were they will be brumating same as the last 9 yrs.
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Jeff Benfer
gartersnakemorph.com

