. . . Go, my people, enter your rooms and shut your doors behind you. Hide yourselves a little while until the wrath has passed. For behold, the LORD is coming out of His dwelling to punish the inhabitants of the earth for their iniquity. The earth will reveal her bloodshed and will no longer conceal her slain.
I think the reason Sept is important, though, is the Jewish holidays.
Rosh Hashana and And Yom Kippur. It seems like those would be days I would expect God to move.
Or maybe the enemy with how much he hates Jews and Christians.