Where are your water lines located? If they are exposed underneath, then IMO 32degF would be where you'd start to worry. If they run behind cabinets or your if your unit is enclosed underneath, then the furnace heat will be very helpful.
Also, even if your trailer is in 32degF air outside and you keep it heated to, say, 60degF, it will radiate heat keeping water lines etc. above freezing. So with a warm trailer, IMO don't panic if the temp dips to 32degF just before sunrise!
Sherm & Terry w/rescue Eydie (min Schnauzer) & Charley (std Poodle)
2015 Jay Flight 27RLS (Nights Camped: 102 '15, 90 '16, 80 '17, 161 '18)
2006 Ford F350 6.0 PSD, 4WD, CC, LB, SRW, Camper pkg, Equal-i-zer, GY Endurance (E)