Joshua 3:15 (KJV) And as they that bare the ark were come unto Jordan, and the feet of the priests that bare the ark were dipped in the brim of the water, (for Jordan overfloweth all his banks all the time of harvest,)
Joshua 3:16 (KJV) That the waters which came down from above stood and rose up upon an heap very far from the city Adam, that is beside Zaretan: and those that came down toward the sea of the plain, even the salt sea, failed, and were cut off: and the people passed over right against Jericho.
Verse 15. This takes place during the flooding season.
Verse 16. At this point the majority of the Israelites didn’t witness the crossing of the Red Sea. Along with that remember the testimony of Rahab saying that we have heard how you crossed the Red Sea and defeated the two cities. Og was the king who was a giant.
So as a sign to both Israel and the land of Canan, God dries up the Jordan River during flooding season. It is like the river hit a wall and started stacking on top of itself like it was forming a pillar that went into the cloud.
Imagine the city watchmen in Jericho. They are standing duty like any other day and they see this mile wide pillar of water forming in the direction of the river. So the watchman sounds the alarm and all of Jericho look towards the event in horror. Everyone except Rahab because she has a promise. Likewise, we don’t know the future,but those who have accepted the gift of salvation through Jesus can live by faith because he have a promise.