Cannabis is pretty cold resistant you don't say where you are but they will pull
thru a frost or two. A plastic tarp should be all you need. Make up some poles to keep the tarp
at least a foot above the plants (no condensation) you don't want mold to get a foothold.
They really look magnificent!
Good luck to you and more pics as you progress please.
keep it green and growing
P.S. Typically NL is a late bloomer.