It's called tunneling. Atmospheric conditions reflect UHF radio waves back to surface instead of allowing them to escape into space. It is not unheard of for people to receive TV signals from 1000 miles away like this. Of course it is only temporary. DXers like to do this and log how many TV stations they can receive.
I used to live in SE New Mexico and have seen TV signals clear as a bell from as far away as Florida and northern California. Lower channels are better for this. That is why low VHF channels can be a problem on digital - far distant stations can interrupt the signal due to atmospheric tunneling.