Hi
What I found MOST difficult about "temporary" GH is the selection of the covering. My worst disaster was using clear plastic with a space heater. Made it through the 30 degree night at 50 When the sun came through it soared to 151 degrees inside while air temp was 65 lol
The BEST at least in my area is "Frostcloth" Generally I can leave it in place for the average 3 day cold period .
Still must be watched close during daytime highs.
Use a colorless infrared bulb for heat source along with a thermostat. Structure made of PVC pipe FC held in place with clips held to the ground with gallon jugs of water. The only thing I still go to such great links to protect is my Vanda orchid "hedge " growing between two queen palms. The ain is temps above 45 but below 80 for the duration. The palms I might add are on their own they supply the support for the structure
Might add that it's VERY important for no leaves to contact the covering . They burn both ways from the cold and the heat.
I had a fairly reliable shadehouse that had a heated aquarium wwhich allowed zones within the structure , Never overheated BUT could not keep up with temps below 40 for more than two hours. Since I had tropical fish in it could not heat above 80 nor allow it to fall below 65.
had great hopes for it but developed a leak so it's now a terrarium lol
If your daytimes stay below 50 you might have a chance
good luck. gary