A nice pleasant hike on a well maintained trail.  There are a couple viewpoints at the top; while the view of Lake Diablo isn't as great as the road lookout, it is much more rewarding.  The area is recovering from a fire; so, while wooded, it doesn't provide full shade on a hot day.  Enough people on the trail, so no wildlife sightings besides maybe an alligator lizard and chipmunks.

We arrived around 11 AM to packed parking lots all around. Cars were parked on both sides going either ways on the road. It was a slightly grey day, but a long weekend, so this was expected.
The trail is in great condition. Such a mellow hike, plenty of kids. We saw a young-ish black bear who was not the least bit interested or fazed by the humans.
Most people would put up their masks when someone approached. Didn’t see any hidden poop bags which gets me really mad, and despite plenty space, most people coming down allowed those going up to pass.

This is a great hike for the whole family! Not too long and not a lot of elevation gain. The highlight of the hike was seeing a bear leisurely have his dinner! Thankful for the pair of hikers that alerted us about a bear ahead so we were able to make the bear aware of our presence. It did not mind us watching for a few minutes while it chose the best berries lol The view at the top is pretty great. I enjoyed a different view of Diablo than the drive up overlook. I will definitely return to this one!

There is some running water over the trail at the beginning when you leave the campgrounds. Waterproof boots were greatly appreciated!

Took a trip up Thunder Knob and then walked along the Thunder Creek trail until we hit the turn up to Fourth of July Pass. 

Nothing massive to note! The trails are both in good condition, aside from a bit of mud. Lots of young kids and older folks so HIGHLY recommend bringing and using a mask when passing to help protect them. I know it's outdoors and it feels a bit silly, but trails are narrow and heavy breathing from a hike sends germs propelling outward.

A lovely trail with a steady but not steep elevation gain and multiple spots for spectacular views. There is a large sign for the trailhead at the campground entrance on the north side of Hwy. 20, with a dozen or so parking spots. The trail starts past the first few campsites. The river was high and over the banks near the beginning of the trail so I splashed briefly. There is one fallen tree that hangs up enough that only children can get under it. It has to be straddled.

On this first day of the general mask order only one of the dozen or more solos and groups I passed had one. But there was room to pass with distance and nearly everyone did so.