Late winter and early spring are great times to visit Yosemite National Park, but be sure to read up on the rules regarding pets before you go. Hotels inside park boundaries don’t allow pets, but pet-friendly places to curl up (click on lodging type and use the pet-friendly filter) are abundant elsewhere in Mariposa County. In Yosemite Valley, the premier winter/spring waterfall hike leads to Lower Yosemite Fall, the most accessible of three stair-stepped cascades that comprise America’s tallest cataract at 2,425 feet in total height.
The paved, half-mile trail from Yosemite Valley Lodge is dog- and wheelchair-friendly, and from the parking lot you can hear the 320-foot Lower Fall roaring like a highway during rain and snow-melt season. You can walk right up to the protective fence bordering the cataract, and both you and your pup can expect to get sprayed when the fall is at full gush!
If you have lots of patience, a good camera and clear skies in mid- to late February, you may be able to catch another waterfall phenomenon known as the Horsetail Fall Firefall. It occurs when sunlight streams through the thin sliver of falling water, turning it molten orange. (Old-timers may remember when park rangers pushed an actual bonfire off a cliff at Glacier Point, a practice stopped in 1968.) Conditions have to align perfectly, and there has to be enough water in the fall for the natural spectacle to take place (it happens just before sunset).
The closest parking to Horsetail Fall is the Yosemite Falls Parking Area near Yosemite Valley Lodge. You’ll have to arrive early, jockey for a spot and keep your dog leashed and on the pavement (with a few exceptions, dogs at Yosemite aren’t allowed on unpaved trails).