Temps in the low 70's, sunny and strong breeze.
This section of the park is infrequently used by hikers and there isn't a "trail" listed on the park maps. The trail I took consist of an old dirt road and numerous cow paths running alongside, and to, the North Concho River.
If you choose to go, go to the North Entrance and park your vehicle at the restroom parking area by the entrance. On foot, leave the park and cross FM2288. You'll see an area where local youths (I assume) park and drink beer. At the fence there is a swing gate you'll go through and at that point, you are in the park again. The old dirt road is visible directly ahead and runs parallel to the North Concho River on your left.
You're able to hike in this area along cow paths and the dirt road for approx 3 miles until you come to the park boundary which is marked by a barb wire fence and a few signs. At that point, you will turn around and return along the same route or you can blaze a new one back to the starting point.
This area is used primarily by hunters so make sure you check in with park personnel to ensure there are no hunts scheduled. This area has the potential to either by very good or very blase. The river is a water source for many animals and birds as well as the longhorns. There are numerous trees in the area so the chance to see birds here that are not in other areas of the park are good IF you're lucky.
Be advised there are no facilities along the trail so bring your own water and food. The longhorns are numerous so give them a wide berth. In addition, on the South side of the river, some of the area is private property - respect the landowner's rights and don't trespass. I suggest you stay on the north side of the river.
NOTES
Water, shade, info kiosk and toilets available at the North Shore entrance restrooms - where you should park.
STRONGLY ENCOURAGE you to talk to park personnel before entering the area due to scheduled hunts.
If you have the time, do a recon using Google Earth to see what the area looks like.