<p>I agree with the advice to look at the individual schools' websites. You need to know exactly when the specific schools you like are open. It doesn't matter if an approximate number of schools are in session, if that group doesn't include the ones you want to visit. </p>
<p>Also, I recommend paying particular attention to the specific dates you may want to visit when looking at the colleges' websites. Sometimes there may be an event or a local holiday that might cause an info session or tour not to be held or might cause some disruption in the normal routine that you'd want to experience. </p>
<p>Some schools will be having exams during the week you mentioned. Probably not the best time to visit, if you want lots of interaction with students. </p>
<p>And keep in mind that some schools, while open in January, may have a winter study, j-term or IAP or some variation on the usual school schedule, and that may not give you the most accurate picture of what life is like there during a regular semester. It doesn't mean January wouldn't be a good time to visit, but you should learn what the schedule is, because there may be more partying and less studying during one of those January terms, and you would want to factor that into your assessment of the school's climate.</p>
<p>Before putting the expense and time into a campus visit, make sure you can go to a class while there. Even is school is in session, if students have just returned or are nearing/doing exams, visiting classes may be impossible or less than helpful to you. Try to get the fullest experience possible. If unsure, cal admissions offices. Most (or maybe all) have toll-free numbers.</p>