Since you don't really know how long the power will be off (-do you even know the reason it's off?) it's always time for concern when power doesn't come right back on quickly, & especially if it's very cold or very hot where you are. 55* outside is fairly modest, but it's not what you want for your BP if your indoor temperatures fall to that, as they will eventually.
For her safety, I'd round up an ice chest (or thick styro-foam shipping box) because they're far more insulated than your snake's enclosure. Also a large cloth snake bag (or pillow case with no holes!), and a rubber band or 2 & some twist-tie wire that's long enough to secure the cloth bag.
Do you have hot water? (ie. is your hot water heater gas or electric? If you have hot water, get 2 large clean jars or plastic water bottles for holding hot water (to use in the ice chest for heat).
Or, if you have chemical hand-warmer packets or those used to ship reptiles, find them & be ready to use them. Wrap them for safety so they can heat the ice chest without contacting the snake, as they can get too hot. Same goes for the "hot water bottles".
When was she last fed? (not sure what is meant by ..."
rest around 36hr ago."?) The more recently she ate, the more you need to keep her temperatures warm enough so she doesn't regurgitate. An unfed BP is pretty good around 75* but one that's digesting you'd want above 80* IMO.
When I used the above described methods to protect my snakes in an ice storm with power off for 4 days ( & while my house temperature got down to 45*) they remained a comfy 78*-80* inside the ice chests, & were calm and oblivious to how badly I wanted to shrink myself to crawl in with them. 
And btw, I only needed to change the hot water bottles about every 8-9 hours to keep them warm enough. That also helped with air exchange- they don't need a lot, but some exchange for safety.
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Obviously, I was typing when you got power back- Yay! But as you said, "for next time".
Originally Posted by Bogertophis
Since you don't really know how long the power will be off (-do you even know the reason it's off?) it's always time for concern when power doesn't come right back on quickly, & especially if it's very cold or very hot where you are. 55* outside is fairly modest, but it's not what you want for your BP if your indoor temperatures fall to that, as they will eventually.
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