Rio de Janeiro is 5 hours ahead of Portland
Best overlap: 8:00 AM to 1:00 PM in Portland is 1:00 PM to 6:00 PM in Rio de Janeiro.
Schedule calls for 8:00 AM to 1:00 PM in Portland — your colleagues in Rio de Janeiro will be online from 1:00 PM to 6:00 PM. You share roughly 5 hours a day. That's enough for regular meetings, but treat the window as prime time and guard it. Remember that Portland shifts for daylight saving and Rio de Janeiro doesn't, so recalculate the overlap after each clock change.