Due to a spell of low temps/storms lately I have left my solar cover on for about 2 weeks (due to pool fencing I have to actually get in it to remove the cover and the water is COLD), been keeping my FC, PH etc in check but my CC is at 1.5. Logic would say that this is because my pool has not been getting direct sunlight to burn it off and it should drop when I remove the solar cover and let the sun hit it but I want to be sure. Do I need to shock or will the CC drop when I expose the pool to light again? Been keeping an eye under the cover every day when I check FC, water is crystal clear.
I'd say keep an eye on it...mine does the same thing if I leave the cover on for a long time, and then it dissipates quickly once the cover is off (without needing to shock).
You get some diffuse sunlight even on cloudy days, and it doesn't really take that much sunlight when there aren't very many people swimming in the pool.