This is the highest board temperature recorded for the IOM during the current sampling window, capturing a brief internal thermal spike the averaged tempAvg would otherwise smooth over. It is useful for catching a transient event, such as a brief traffic-load spike, that a longer-term average would not reveal. For example, a tempMax notably higher than tempAvg in the same window could reflect a brief burst of high traffic load through the IOM's ASICs generating a short-lived heat spike.