I would get some silicon grease from a plumbing supply and put a light coat on the rubber gasket.

I bet the blinker fluid tank leaked and since it was cold it froze your trunk lid seal closed.

Clean it with soap and water. Dry it completely. Then apply a silicon based lubricant to the weatherstripping. Problem solved. For a while, anyways.

A light coat of K-Y usually does it for those dealing with trunk problems.

+1, I do this with all my weather stripping. I use a silicone spray.

trunk monkey, problem solved.

wax the trunk lip where it contacts the rubber, just wipe on a good coat and leave it, don't buff.
use the silicone spray on the rubber.

should keep it opening for a while.

If it is frozen shut and you need it open maybe spray it with windshield de icer around the edges

I always wondered if it was good for anything else.

Use a solution of 50% rubbing alcohol, 50% water. I keep a bottle in the garage for when I need to de ice my windshield before heading off to work. Two car garages are a joke. The silicone jelly trick will work, but needs warmer weather to evenly apply. I do the weather stripping on my drivers side door every fall because it sticks in cold weather after a freezing rain.

Good ole vasoline works just as well and less expensive

K-Y Jelly sounds better.

I had one of those. Hated my wife and fought with my dog. Won't keep anything that fights with my dog.