how soon can you contact PIs?

I have already started a list of PIs I want to work with, read their papers etc and people usually say to contact them as early as possible. However, I am insecure of contacting them right now, since it is interview period for some schools and if they are in the admissions committee my email might not be read with too much gusto. So, when can you start contacting PIs for 2025/2026 cycle? Would mid-March be an acceptable date?