College application season is not what it used to be. Historically, due dates were in January. Now early application and early decision deadlines begin in the fall, as early as October 15. Some of my students were able to apply to colleges in the summer after 11th grade and got acceptance notices before their senior year began.
Whether a student applies early or not depends on their ability to get applications and essays ready by fall and when they want to know their admission decisions. Early applicants find out early if they are in or not. That gives them more time to apply to other colleges during regular decision, if desired. Early admission applicants also have the luxury of having the time to get the best grades in their senior year and have time to apply for scholarships.