This is the historical record of the peak ambient temperature reached during a specific past sampling window, preserving a spike that might otherwise be lost once the live IOCardStats row moves on to newer data. It is specifically useful for after-the-fact investigations, since the live stats table only ever shows the current window's peak, not what happened hours or days earlier. For example, reviewing ambientTempMax across historical entries from the night of a reported cooling event would show exactly how high the temperature spiked before cooling was restored.