My rear driver side strut/shock acts up depending on the weather

I have an 86 Toyota Tercel.I live in the Pacific NW.We pretty much have one season,rainy.My car is fine when it’s rainy,about 8-9 months of the year.It doesn’t rain in summer.A few weeks after it stops raining my rear driver side tire makes a clunking sound when I go over a bump.It goes away as soon as it starts raining again.The past two winters have been very cold,it got below freezing a few times.If it stays below freezing for more than a day or two,it seems like my strut(or whatever it is) freezes too.If I go over a bump I feel like I don’t have a suspension system at all.Any ideas?