Summer, Fall, Winter, Spring, any season is open for Marfa Lights to go hunting at night, at least according to the hypothesis of bioluminescent flying predators in southwest Texas. But they do prefer warmer nights, or at least nights that are not so cold, according to many years of data collecting by James Bunnell, author of Hunting Marfa Lights. (Be it understood, Bunnell seems hesitant to admit the possibility that the CE-III lights themselves go hunting; he has been looking for non-living explanations.)
Marfa Lights of southwest Texas . . . are seen only a few times each year. They appear only at night, but at any season, with little regard for weather, with one exception: They prefer glowing on those nights that are not too cold.
The problem for those scientists who look for a non-living explanation—that jumps out from the dark when we examine details from Bunnell’s data on temperatures, an enlightening exercize. Ground-temperature coorelation fails fit a non-living hypothesis, for a large proportion of sightings occur in Spring, when the ground has not much warmed up from winter. Air-temperature coorelation likewise fails, for it does not explain why the rarely appearing CE mystery lights sometimes occur at about the same time after sunset on consecutive nights, when those nights have varied temperatures recorded (not to mention other variations in weather on two consecutive nights of sightings).
How do generally-less-cold nights relate to the possibility of living pterosaurs? The coldest nights would not only be more stressful for nocturnal hunters, they would be more likely to cause prey to be hidden deep underground, making it more difficult for predators. The hypothesis predicts predators would hunt more often, during winter, when the temperature was not too bitterly cold, and the data coorelates with this quite well.