In the spring I replace numerous burst freezeproof faucets because the hsoe was left on all winter. Then once you turn it on to use it in the spring it starts to leak.
I remember two decades ago listening in horror as the town utility maintenance superintendent attempted to explain on the news the aftermath of the worst blizzard I can recall. When asked why all these leaks had appeared when we thawed out, he winged it claiming that, "when the weather warms it pushes the cold deeper into the ground, freezing more lines." Oh, brother...
It never occurred to thim that ice is an effective plug, so he came up with some alternative theory that violated the 2nd Law of Thermodynamics.
EDIT: I should add for the OP that we had one of these yard hydrants (or very similar, topworks was red, layout looked the same) during that blizzard and it did not freeze. We had everything buried below the frostline. We might have crudely insulation wrapped the hydrant during the coldest portions of winter when we were not using it--I'm not certain but have a vague recollection of that. Probably wouldn't hurt to put some cheap pipe insulation onto the vertical pipe since it will conduct cold down toward the buried frost line.