This is the historical record of the lowest ambient temperature reached during a specific past sampling window, the floor counterpart to that period's ambientTempMax entry. Like its live counterpart, it is mainly useful for spotting an anomalous, implausibly low reading that suggests a sensor glitch happened at that point in the past rather than a real event. For example, a single historical ambientTempMin entry far below the surrounding entries, with no corresponding real-world cooling event, would point to a transient sensor error rather than an actual temperature drop.