Freeze damage happens when air or pipe-adjacent zones stay below 32 °F long enough for water to expand. Garage probes measure air, which is usually a few degrees warmer than fluid in an exterior wall cavity—so build margin into any alert threshold.
Choosing thresholds
Many owners watch for sustained air temps below 35–38 °F rather than reacting to a single 31 °F blip during a door opening. Review history browsing for overnight plateaus, not spikes.
Zone-specific rules
- Door-adjacent probe: Expect brief dips; do not treat every spike as emergency.
- Interior / pipe-wall probe: Tighter threshold; this zone best represents risk.
- Average key: Useful summary but can hide a cold corner—check individual zones.
Related monitoring
Understand drivers with seasonal patterns and infiltration. Hardware reliability matters too—DHT22 retries prevent false alarms from bad reads.