The pre-flood vapour canopy was created on day 2 of Creation when God divided the waters from the waters. Evolutionists will rubbish it as it plays havoc with their dating methods. This high temperature region is about 80 miles above the earth's surface. Russian astronauts discovered this in the fifties, and noted that this region would have been capable of holding superheated steam. This aqueous canopy encircled the early earth, which was a paradise for man , beast and plant. This canopy protected the earth from harmful radiation and greatly enhanced health by reducing mutation rates. The atmospheric pressure on earth was higher (hyperbaric), this would lower metabolic rates like breathing and heartbeat. The oxygen content was also higher than today, which was very beneficial to health, -(pre-flood fossil finds show air bubbles trapped in amber with an oxygen content of 30%.) The canopy would have given a uniformly temperate climate around the earth, there were no atmospheric ciculations like today, ie -no wind or rain , which is consistent with Scripture. There were no frozen Polar regions -(fossil finds have shown tropical plantlife existed once in these regions). There was no volcanic activity till after the flood when the earths crust was broken up, originally it was all one land mass.
Just in finishing -God made no pronouncement about the second day, i.e. He didn't call it good, -I guess He knew what He had created would be used to destroy the earth in the Flood.