I left my hibiscus out in pots and temps fell below 30 degrees a couple times, but they were covered and the dogs thought that it was their bed. How and when will I know if they are dead cause my Cotton Rose hibiscus made it through the winter in a pot alongside the larger ones-- strange winter in Florida.
Hibiscus Out All Winter
Certified GKH Gardening Expert
Wait until spring to cut back the plant, which will help protect the new growth, just in case another freeze occurs. These articles will help you as well: