What does it mean that the days will be as the days of Noah?

When Jesus spoke of His coming being "as the days of Noah," He was describing the spiritual condition of the world right before He returns. In the days before the flood, people were eating and drinking, marrying and giving in marriage, going about their normal routines, right up until the very day that Noah entered the ark. Life seemed to be going on as usual, with no sense of urgency or awareness that judgment was about to fall.

The key detail Jesus highlights is that they "knew not until the flood came, and took them all away." The people of Noah's generation were not necessarily wicked in some obvious, dramatic way in that moment, they were simply unaware and unprepared. They were caught up in the everyday business of living and were caught completely off guard when the flood arrived and swept them away without warning.

Jesus says, "so shall also the coming of the Son of man be." This means that when He returns, the world at large will likely be in a similar state, carrying on with life as usual, marrying, working, eating, with no real expectation or preparation for what is about to happen. The suddenness and the unpreparedness of the people in Noah's day is the pattern for how the world will be caught when the Son of man comes.

This is why the surrounding teaching calls believers to watch and be ready, since the exact hour is unknown even to the angels, only the Father knows. The comparison to Noah's day is meant to warn against complacency and to encourage readiness, so that His coming does not catch His own people by surprise the way it will catch the rest of the world.