How do I set up a freeze alert in Home Assistant?
Create an automation with a numeric state trigger on your temperature sensor, below 35°F for 10 minutes, and a notify action to your phone. The catch: if Home Assistant or your home internet is down, the alert never goes out, so pair it with something that notices when readings stop.
The automation
Replace the sensor and notify service with your own. The 10-minute delay stops a brief draft from alerting. This assumes Home Assistant is set to °F; use about 2°C if it is in Celsius.
automation:
- alias: Garage freeze warning
triggers:
- trigger: numeric_state
entity_id: sensor.garage_temperature
below: 35
for: "00:10:00"
actions:
- action: notify.mobile_app_your_phone
data:
title: Freeze warning
message: "Garage is {{ states('sensor.garage_temperature') }}°"The weak spot: when Home Assistant is the thing that fails
A power cut or internet outage is often what lets a space get cold, and it also takes Home Assistant or its connection offline. The automation cannot warn you about the outage that disables it.
An off-site service covers that gap. ProbeHarbor, for example, can receive the same readings from Home Assistant and alerts you both when it gets cold and when readings stop arriving. On Devices → Setup, choosing Home Assistant generates the YAML with your key.
Frequently asked questions
Can Home Assistant send a text message for a freeze alert?
Yes, through a notify integration for an SMS provider such as Twilio, or through the companion app for push notifications.
Which sensor should Home Assistant use for freeze alerts?
Any temperature sensor near the pipes works: ESPHome with a DS18B20, a Zigbee sensor, or a Wi-Fi sensor with an integration. Placement near the coldest pipe matters more than the brand.
Related
Get a freeze alert for your space
ProbeHarbor watches probes in garages, crawlspaces, and cabins and alerts you before pipes freeze. The free plan includes email alerts; bring an ESP32 probe or connect Home Assistant.