I, like most of my fellows, prefer my meals served piping hot. As all know, humans sometimes feed their dogs table scraps. If I put down a small piece of chicken from within a piping hot chicken pot pie and alert my small pet dog that it's for her, she'll stand back 2 or 3 feet away from it for a while before eventually consuming it. I am starting to believe that she only does this behavior when the food I put down is too hot for her. So it begs the question I here pose: are dogs able to see heat radiation from afar?
A dog's nose can even sense weak thermal radiation, as found out recently by researches at at Lund University and Eötvös Loránd University. So strong thermal radiation can be detected from a couple of meters away which would explain your observations.
Citation from this article:
To test the idea, researchers trained three pet dogs to choose between a warm (31°C) and an ambient-temperature object, each placed 1.6 meters away. The dogs weren't able to see or smell the difference between these objects. (Scientists could only detect the difference by touching the surfaces.)
After training, the dogs were tested on their skill in double-blind experiments; all three successfully detected the objects emitting weak thermal radiation, the scientists reveal today in Scientific Reports.
Next, the researchers scanned the brains of 13 pet dogs of various breeds in a functional magnetic resonance imaging scanner while presenting the pooches with objects emitting neutral or weak thermal radiation. The left somatosensory cortex in dogs' brains, which delivers inputs from the nose, was more responsive to the warm thermal stimulus than to the neutral one. The scientists identified a cluster of 14 voxels (3D pixels) in this region of the dogs' left hemispheres, but didn't find any such clusters in the right, and none in any part of the dogs' brains in response to the neutral stimulus.
Together, the two experiments show that dogs, like vampire bats, can sense weak hot spots and that a specific region of their brains is activated by this infrared radiation, the scientists say. They suspect dogs inherited the ability from their ancestor, the gray wolf, who may use it to sniff out warm bodies during a hunt.
Here's the scientific article if you want to dig your nose in a bit further (pun intended)..