Death Valley National Park is home to sand dunes and salt flats,canyons and badlands. From late fall to early spring, expect pleasant daytime temperatures.
At Joshua Tree National Park, you may feel like you've stepped into a Dr. Seuss story book! Visit from late fall until spring for epic hiking. The stargazing here is superb too.
Lassen Volcanic National Park contains all four types of volcanoes and many cool hydrothermal features. Visit in the summer, when the park road is generally open.