None. Our trailer is gel coated and is 13 years old with all of it spent in Michigan winters for a while. It is here right now with temps in the low 20's and lower getting ready to leave for warm weather next week. No gel coat problems in all those years.
Here is a picture of my son-in-law helping me dig it out last Sunday to bring home to load for the trip.
Barney
2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine