There is no official closure for this trail, but since it follows a serious drainage, its best to wait until late in the season before hiking. Otherwise the trails are very muddy.
Cow Creek Loop Trail departs from the Summit Parking area and connects to Headquarters. It starts as a rolling and steady descent through a drainage that offers some great views, and on occasion some wildlife. The trail is very smooth with few rocks or roots. Early season the trail is very muddy, so it is best to wait until July (or sometimes later) for the trail to dry.