Wise words from Bill.
I start to harvest parsnips very early, using them as baby veg. This is when they are about the thickness of a good cigar. They are tender and tasty and the thinning gives others room to get bigger. But as we get into early autumn I stop harvesting and await some cold weather before I harvest more.
Don't give up yet. They can sit undisturbed a bit longer and you can try them again later. Nothing to lose by waiting, although, of course, no one can be sure if winter will be a mild one or a cold one.