It's not too late to pick an event and go. https://forums.njpinebarrens.com/threads/state-park-service-first-day-2018-hikes.12401/
Bass River SF's event is at West Pine Plains, starting at NJ-72 and the eastern boundary of Coyle Field, 7 miles, daytime forecast high temperature is "near 18" degrees. (High temperature. Not overnight, not windchill, actual temperature. Wow.) I'm pretty sure the hike leader is not going to cancel. I think about 16 people signed up so far. Limit is 25 and registration is required but the office is open Saturday so you can still call to register. Some of the other events don't require registration and you can just show up.