There were lots of things that went into the formation of weather. But the one key factor was air pressure, something which Ed could not say was missing from the dungeon.
'I do often feel the wind so there must be air pressure… right?' But could he apply the common sense of his previous life to the dungeon? Everything in there appeared to happen at the whims of the dungeon.
'Even the day and night cycle likely relies on the dungeon' Simply put everything felt like a real-world but was ultimately artificial. The dungeon must have recreated everything based on whatever it knew on the outside world or at least what it knew was necessary for the growth of life.
But that begged the question of how it knew these things…
'The system could have told this dungeon, but what about other dungeons?' There were dungeons with suns and moons, so did they also have a system? If they needed to first learn about them from the humans who attacked them all first floors would be dark and undead.
