Ce n'est pas une question de température :
Theories of origin
One possible naturalistic and scientific explanation for such phenomena is that the oxidation of hydrogen phosphide and methane gases produced by the decay of organic material may cause glowing lights to appear in the air. Experiments, for example, done by the Italian chemists Luigi Garlaschelli and Paolo Boschetti, have replicated the lights by adding chemicals to the gases formed by rotting compounds. Critics claim that this theory does not easily account for reported cases which claim lights bob, swoop, soar upwards or downwards, or move against the wind.
William Corliss writes, in Remarkable Luminous Phenomena in Nature (Sourcebook Project,[1] Glen Arm, MD, 2001:290): "No satisfactory mechanism has been demonstrated whereby gases escaping from marshy areas will spontaneously ignite. Furthermore, most low-level nocturnal lights are cold—not what one would expect from burning methane. Also, no one has explained how clouds of luminous gas can maintain size and shape while engaging in erratic maneuvers over many minutes."
Others believe bioluminescent effects (e.g. honey fungus) cause the light. Other explanations include causes similar to ball lightning.
(...)
Other similar theoretical explanations, however, involving light emanating from naturally occurring electric currents do not involve pseudoscientific elements. Also, electric-based theories more easily account for the claimed seemingly free movement of the lights and claims that the lights react upon the introduction of nearby objects (e.g. humans).
Another theory was put forward claiming these lights are barn owls with luminescent plumage. Hence the possibility of them floating around, reacting to other lights, etc. See A Review of accounts of luminosity in Barn Owls Tyto alba.