Hurston's writing style in Their Eyes Were Watching God is highly literary and figurative, despite the informal-sounding dialect that we hear all throughout the dialogue. So it's natural to notice that similes play a significant role in her literary writing style.
Let's look at a few examples.
In Chapter 1, as Janie returns to her hometown and causes a lot of nasty gossip, we see a beautiful simile:
"Seeing the woman as she was made them remember the envy they had stored up from other times. So they chewed up the back parts of their minds and swallowed with relish. They made burning statements with questions, and killing tools out of laughs. It was mass cruelty. A mood come alive. Words walking without masters; walking altogether like harmony in a song."
Here, the narrator is not only personifying those mean words of gossip, but she's also using a simile to say that the words are "walking" in a way that reminds you of "harmony in a song." The simile helps us grasp how there are multiple people saying awful things about Janie (because it takes multiple people to harmonize while singing) and that the rumors are all in agreement with each other (because sounds sung together in harmony sound nice together even though they're different tones).
Soon afterward in that first chapter, people can't get over how physically beautiful Janie is:
"The men noticed her firm buttocks like she had grape fruits in her hip pockets; the great rope of black hair swinging to her waist and unraveling in the wind like a plume..."
The narrator uses these two similes right in a row. We're told that her backside looks like fruit, which implies that Janie is healthy, beautiful, and desirable; and we're told that her beautiful hair looks like a plume (a tuft of feathers), which implies that Janie might share some characteristics with a beautiful bird—we'll have...
to read further to find out if she preens, if she chatters, if she figuratively flies free, and so on.
Let's look at one more simile to finish getting a sense of Hurston's literary style. Chapter 2 opens with this one:
"Janie saw her life like a great tree in leaf with the things suffered, things enjoyed, things done and undone. Dawn and doom was in the branches."
By comparing Janie's life to a tree with leaves on it right now, Hurston emphasizes how Janie's life has endured seasons of change. She’s gone through periods of happiness as well as periods of struggle.
As you can see, although it's great to notice the similes and understand what they mean, it's even better to ask yourself, "What does this comparison reveal?" or "Why is this comparison appropriate?" Answering those questions for yourself really helps you dig deep into the characters, the story, and the author's style.