Mormon does not report what phenomenon allowed the night to appear as though it were no night. I have suggested that a type of volcanic eruption might provide enough light to qualify. (See commentary accompanying Helaman 14:3–4.) Volcanism would be noticeable, natural, localized, and culturally significant. Regardless of the cause or how modern readers might have seen it, the important point is the Nephites’ interpretation of the phenomenon. It is worth requoting the passage from the Florentine Codex already quoted in the commentary accompanying Helaman 14:6:
Ten years before the Spaniards arrived here, an omen of evil first appeared in the heavens. It was like a tongue of fire, like a flame, like the light of dawn. It looked as if it were showering [sparks], as if it stood piercing the heavens. It was wide at the base, it was pointed at the head. To the very midst of the sky, to the very heart of the heavens it stood reaching; to the very midpoint of the skies it stood stretched as it was seen. It was there to the east when it thus came forth at midnight; it looked as if day had dawned, day had broken. Later, the sun destroyed it when he arose. For a full year [the sign came forth].
Here is historical evidence that people in that area saw signs in the heavens which made night as bright as day. This passage is not necessarily evidence of the lights themselves, but it documents that at least some Mesoamericans accepted that such a phenomenon was possible and that it had a divine significance. Although the Florentine Codex describes the Aztec period of approximately A.D. 1500, it is not hard to understand how the Nephites might have likewise believed in and described a similar culturally significant phenomenon.