Sorry for the delayed response. I just saw this.

It is in the 20s here now and no problems. It was single digits a week ago and still ok. They have not frozen up on us at all.

The PetSafe company stands behind their product as well. I had a PetSafe collar that stopped working 11 1/2 months into the 12 month warranty. They sent me a new one without a lot of back and forth. Just an apology and a new one in the mail. What's not to love about that?! This is why I bought a Pet Safe door. I have a collar for the other dog and no problems at all with that one.