Although few people do the following, it will work:

Keep the plant outdoors in a warm site as long as freezing weather isn't predicted.

In the event of cold, bring it indoors, even if only into an unlit garage. Return outdoors when it's again warm.

The above assumes it's in a pot.

If not, you can protect it on site.

I've used several layers of frost blanket. And when it was truly cold, I put a 60-watt work light on the ground underneath the frost cover. Keep the light on as long as needed, even if for several consecutive days.

Dear Reimi,
Did your tropical hibiscus stay outside all winter? That would be amazing!
Tropical hibiscus can also be saved by taking cuttings and rooting them in a pot covered with a clear plastic bag.