Well i don't know about temp spike but i do know they can handle very low temps
when i hatched out my last buttons back in september 08
the last 3 days of incubation i thought i was turning the temp UP when in fact i was turning the temp DOWN so down it was at 43 for the last 3 days of incubation.. well finally on day 19 two days after there hatch date i realize i was turning the temp down..
so i turn the temp up got it to 100 and within 5 minutes all the buttons were out