I doubt 27 will be a problem one night for your tank ... HOWEVER, I usually put a 60W light on a service cord in the wet bay to help keep the temperatures up a bit above freezing. My RV has furnace duct-work into the wet bay so I have the alternative choice of just leaving the furnace on, too, to keep the tank area above freezing.
Ed - on the Central Oregon coast
2018 Winnebago Fuse 23A
Scion xA toad