Is it possible to attend two community colleges in one semester?

Yes. But you can receive federally-based financial aid at only one school per semester.

Your question doesn't say whether you mean "at the same time" or "if you transfer from one to the other." You can certainly attend both at the same time in most situations. If you get admitted, meet all requirements, and work out a schedule that allows you to make it from one school to the other, there is probably no reason why you couldn't take classes at two different community colleges. The question about transferring is a different matter. You would most likely be transferring into "college number two" at a point much too late in the term to catch up on missed work. Community colleges generally have a deadline for joining a class, and after that point, you would not be admitted.