While most UC campuses *primarily* admit students for the fall term,
some UCs *do* allow transfers in the spring, but it's much less common than fall admission. The availability of spring admission varies by campus and by major. You'll need to check the admissions requirements for each specific UC campus you're interested in. Their websites will have the most up-to-date information.
In short: It's possible, but not guaranteed, and you should expect a more limited number of spots and a more competitive application process compared to fall admission.