We took a church youth group on this hike, ages 11-17 years old.  This is a great hike for beginners.  The hike itself was uphill almost the entire way, but there were benches along the way.  I don't remember seeing Diablo Lake until the very top.  Great view at the top, with lots of room to accommodate lots of people.  However, the edge felt a lot closer than I would have liked.  (Did I mention it was a group of 11 teenage boys?)

This was a nice Tuesday afternoon hike after a lot of rain. I had plans to do a lot of hiking in the North Cascades but unfortunately rain and wildfires pushed me to backup plans. I’d categorize this hike as easy, but the views were definitely great! The clouds never fully lifted off the top of the snowcapped mountains we got views of along the trail, but Diablo Lake was stunning. Would recommend for an easy/short hike if you’re in the area! Could definitely be done after a longer hike in the area during times of good weather. Parking area right along the lake is a bit small, although we had no problem around 2:30pm on a Tuesday afternoon. 

Easy hike with beautiful views! My fav hike thus far in Washington. Arrived at the trailhead around noon and had no issues with parking. It was high 80s when I hiked so the swim in Diablo Lake felt amazing. Would recommend.

A beautiful warm to explore in the mountains. We arrived at the trailhead around 10:30 and there was still a few spots left in the gravel parking for thunder knob. We decided to park across the street at the lower colonial creek campground. The bathrooms by Thunder Knob are all closed. The trail is a mix of switchbacks and long stretches. Flowers blooming including our favorites red columbine and tiger lily. We didn’t notice the tiger lily until the way down and my 4 year old was so excited. Don’t be fooled by the temperature when you get out of the car. We were overdressed and plenty warm. In the forest and by colonial creek it is cool and feels great. But that is less than 1/3 of the entire hike. Most of the hike is in the sun with little shade. Make sure to bring water if you go on a hot day. The trail is very rocky. Lots of of loose rocks and a few areas that can be ankle twisters. But otherwise the trail is in great shape. It does seem like you reach the top a few times but then turn a corner and are like, nope. There are benches all around. I think around a dozen including 6 at the top. The views were amazing. A great day overall. 

An easy hike and a good option to stretch your legs or when hiking with kids, but the views weren’t any better than what you can see from the car lookout so I wouldn’t necessarily recommend for people with other options.