The times are so bad at this point, Jesus Christ says not even to come down and get one's clothes. How can a person, in coming down off his housetop, not go through his house and pick up some clothing? The answer involves the way the homes were built in Jerusalem. It was entirely possible to run from one housetop to another because they butted up against one another. The top of the houses were built flat, and the people used it in the same way that we would use a patio. In the cool of the evening, they went to the top of their house and sat there and talked to their neighbors on the adjacent rooftops.
So if a person were on his rooftop when the time came to get out of Jerusalem, he could literally run from housetop to housetop to housetop without ever coming down on the street for a long distance. Such a thing would never happen in the U.S. and Canada. But, nonetheless, it conveys an intense sense of urgency. If indeed a person happens to be there in Jerusalem at that time, he would have to flee immediately for his life.
The question always arises, "Was this fulfilled when the Temple was destroyed in AD 70?" It is interesting when one looks into church history (apart from the Bible), though not necessarily true church history - call it "secular church history," in which the people call themselves Christians but their doctrines do not conform to the Bible. These people left a record of events of the time. The church historian, Eusebius, had this to say regarding the true church in Jerusalem during the period between AD 66 and 70:
That it [the church] was instructed to leave Jerusalem and take up residence in one of the cities of Perea.
The church did not flee in the sense that Jesus means in Matthew 24. It migrated from Jerusalem to one of the cities of Perea, Pella. Pella is not in a wilderness area but one of the cities of the Decapolis. Decapolis means "ten cities"; there were ten small cities in a small area right around the Sea of Galilee. It is not in the mountains, though it is near some. The church probably left somewhere in late AD 69. If they had left earlier than that, they would have run headlong into Vespasian's army, because Vespasian's army was stalled fighting in the area of Galilee. In AD 69, Vespasian was recalled to Rome where he was crowned Emperor. His son Titus took over the army and came down on Jerusalem. Now by moving his army toward Jerusalem, it became safe for the church to migrate away from Jerusalem.
Josephus records that on the Day of Pentecost, while a great multitude was in the Temple, the people heard a voice say, "Let us go from hence." The church, then, left in an orderly way without urgency, migrating to the area of Pella. This is the exact opposite direction the Bible indicates the Place of Safety is located. So we would have to conclude that what happened in AD 66-70 was a "type" of the church being removed to a place of safety so that it could survive. However, it was not what Jesus was talking about for the end-time church, when some will flee with such urgency that they do not even come down into their house for their clothing.