The feasibility of an underground LoRaWAN bushfire temperature sensing node from the point of view of survivability in a bushfire event is considered. Thermal penetration into the soil is modelled using a one-dimensional analytical formulation for a semi-infinite solid. A working prototype of the sensor unit was tested experimentally beneath a relatively small (400 mm × 400 mm base) timber fire. A buried LoRa radio (depth 100 mm) with a k-type thermocouple monitored the temperature from beneath the fire. The analysis demonstrates that under dry soil conditions, the time that the sensor node under the fire base can endure is proportional to the square of the depth of burial of the electronic components and inversely proportional to the thermal diffusivity of the soil. The original contribution of the work is in the practical demonstration of the durability of a LoRa sensing node beneath a fire front for bushfire sensing applications.