Vernal Fall is Yosemite National Park flows: all year, though by mid to late summer, it narrows and separates into one, two, or three falls as water flows decrease; peaks in late May. You can also hike to Vernal Fall on a moderate 1.6 mile (roundtrip) trail to the footbridge that's rated moderate. The full 3 mile roundtrip hike to the falls is strenuous to the top and not advised for younger children. The trailhead begins at Happy Isles (shuttle stop #16)
I remember hiking this trail as a teenager and thinking, "it's only 1 mile to the top of the falls", and then once I was at the top thinking, "that was the longest 1 mile I have ever walked!"
The trail starts off directly on a steep uphill incline with impressive views of the rushing river below and a look out view of Yosemite Falls across the valley floor. You will pass impressive rocks, lots of trees and squirrels until you reach the bridge at the half way point. The bridge offers a spectacular view of Vernal Falls. There is water and a bathroom here, lots of people and lots of squirrels.
The next section of the trail offers about 200 stairs and sharp drop offs to the river below. When the falls are full, the stairs can be wet and slippery and you may get drenched. When you reach the destination at the top prepared to be impressed. What a beautiful view of the thundering water pouring over the edge of the cliff!
Surprisingly, the trip DOWN can be HARDER. Your muscles are fatigued and they have to work hard at stopping your downward momentum. Hard on the knees and thigh muscles.
Despite it being a LONG 1 mile, I have hiked this trail many times since I was a teenager and have loved it every time. My feet and legs have always complained the next day, however!
p.s. We took our two oldest boys to the top last summer (9,7) They made it with a lot of encouragement and bribery. They enjoyed it, but it was very hard work. They said later that they never want to do it again. We trust they'll change their mind when they are older and stronger. So think carefully whether your kids are strong enough to get enjoyment out of this hike!
You don't have to hike all the way on top of the falls as that may be difficult with young kids. But you'll find an excellent view of Vernal Fall from the footbridge already (1.6 mile hike round trip). It's worth the hike! We hiked it with our 1 year old son and had fun!