Most require that you are a junior or at least 16 years of age, none of which I am. I understand that there are still programs at Harvard, Cornell, etc but those do not provide credit. The for credit programs are all restricted to juniors.
Columbia has some summer programs open to rising sophomores, but I don’t think they provide credit. I filled out the application freshman year, but actually ended up traveling with my family so I didn’t submit it.
I’m not sure how many for-credit programs there are for freshman, if any, but if you can’t find one I’d definetely still recommend a non-credit program. So much fun and you learn without all of the pressure. 
Have fun no matter what you do this summer!