Arrived at trailhead around 12 noon. The lot just outside the campgrounds were full so we parked across the highway where there was some space to park. (There is also a another campground a large parking lot on this side as well.)

Since campground is closed, the restrooms are closed but there is an outhouse that was open. Did not use but saw others had so know it was open. 

We passed a handful of other hikers/groups on our way up. And saw many coming up as we headed back to the car but it was quite spread out so I didn't feel like it was ever overcrowded. It took us about an hour to trek up with a toddler on my back in hiking backpack and a dog who likes to stop and sniff around. We lucked out because when we went to the lookout at the very end where there are two benches, no one was there so we had a nice peaceful time. My toddler's take: It smells nice here. (Yes, the pine did smell nice.) Shortly thereafter, many other hikers arrived at the top but since there is space to sort of go down on the rocks to get a view away from the benches, it's not like we were all huddled in the immediate same space. We took our time up here and enjoyed our snacks and hydrated. We've done this hike before in the snow and didn't realize how big this view point area actually is. (There is also a first lookout area with benches that others had stopped at but we passed this to go on to "the end.")

Lots of other well-behaved leash dogs out. Just remember that while the start of the hike has coverage because of all the trees, the second half up is pretty much all exposed so you are in direct sunlight on a sunny day like today. 

We did see one large group of adults and kids go off trail and hike "straight up" rather than stick to the trail and do the switch backs. This wasn't an area where someone may have mistaken it for trail. It was clearly brush and gravel and not a trail :(

Some nice red and yellow fall foliage here and there throughout the hike. When we returned to our car about 2.5 hours later, there were way more cars and people around. Not only was that lot just outside the North campgrounds/trail head completely full still, there were cars parked on the shoulder down both sides of the highway - some quite precariously. I think it gets crowded here because not only are people parking to hike, others are also going down to the lake. 

Anyway, this is a great hike for all ages - we saw other families with young kids to a group of teens and many young and older adults. 

The last time we went up to Thunder Knob, it was raining and cloudy and when we reached the viewpoints at the end of the trail, all that could be seen was clouds.  Not so this time, as it was a lovely day for a walk. Plenty of people on the trail and the parking lot was full when we started and when we got back

Trail was in great condition, although a bit rocky for the dogs liking.  They were a little apprehensive about crossing the metal bridge at the beginning of the trail, but they overcame their fear and made it through.  The climb is really gentle because of the multiple switchbacks.

There was a little bit of color on the trail, primarily with smaller bushes, but it will be awhile before trees reach full color.  The views from the lookouts were outstanding and as others have pointed out, the colors of Diablo Lake are otherworldly.  You could clearly see how the Sourdough Fire hopscotched through areas of the mountain.  The fire did not seem as extensive as was originally feared.  

Overall, a great hike.

Trail well marked.  Parking area is easy to find but parking is sparse.  Trail was remarkably easy to walk.  Lots of loose rock though so hiking poles could be helpuful.  Views are spectacular in every direction!

Hike Rating: 8.  Short hike with gradual ascent leading to beautiful view of green forested mountains, snow covered peaks and unbelievable stunning turquoise waters.  Seriously, the color almost looked fake.  There was a wildfire nearby and we watched helicopters and planes fly up the ridge to dump water on the fire.  So fun  to watch.  We stopped at the park visitor center in Newhalem after the hike and listened to a Ranger Talk on this fire and wildfires in general.    Very interesting. 

The trail was as described, and very nice. We arrived at 9:30am and the here were plenty of vehicles already, but found a spot no problem. As it’s a popular hike we saw quite a few people, but not congested. The views as described are well worth the effort. We had rain to start, and rain to finish, with sunny conditions in the middle. The mountains held onto the clouds but still very nice for pictures. My wife has a chronic bad back so this was a bit of an effort but managed. Would recommend this hike to anyone of all ages and abilities.