I’m glad that the Fibaro has worked for you, but it is only rated down to 0°. Not below.
One option to consider is the Kumo wireless tag sensors. They are rated for between -40°C to 85°C. They’re a good quality device and there is a community – created integration, or you can just use IFTTT
The problem is that they require their own bridge device, so that increases the cost, as the bridge is about $60. It can support up to 40 of its own tags. And then the sensor is another $39.
So a more expensive option, but one that is warranteed for a much wider range of temperatures.
I know there are some EU community members who have them, but I don’t know if they had to write to the company about special shipping.