As I thought about it, my initial thought was that they probably aren't jumping out of trees on purpose, but maybe they are falling out of trees from time to time. As I thought about it more, I really got intrigued. Especially after reading that ticks can apparently fly short distances, I decided to do some research.
I landed on some information from the folks at Kansas State University, who did some tick mythbusting in a post to their website a few years back.
In their post, they explained that a lot of people believe that ticks can end up landing on people out of trees, but the idea of ticks raining out of trees is more of a bad dream and less in the realm of reality.
When it comes to the idea of jumping out of trees onto people, they explain that ticks can't jump or leap. "They have no physical mechanism to do that". Furthermore, while some ticks have eyes, some don't. Even the ones with eyes can't see particularly well, and wouldn't be able to strategize a jump from a tree. Generally, they just crawl around using sensory organs that detect carbon dioxide and heat, which are signs of a host to feast on.
What about falling out of trees?
The folks at K-State say there is no evidence that suggests that ticks climb way up trees, which would cut down on the possibility of a tick even accidentally falling on you and getting a free lunch.
All of the evidence points to ticks being perched up on blades of grass, leaves, or lower twigs waiting to climb aboard when you come into contact with them. They say that the most likely way a tick ends up on you is by crawling up the back of your pants and shirts and looking for skin, where they then find a place to bite.