Because in the one the severity of the cold prevents your flight to the deserts, and your lurking in mountains and wilds; in the other, you must either transgress the Law, if you will fly, or encounter instant death if you will stay.
Chrys.:. Note how this speech is directed against the Jews; for when these things were done by Vespasian, the Apostles could neither observe the Sabbath nor fly, seeing most of them were already dead, and those who survived were living in distant countries. And why they should pray for this He adds a reason, “For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor shall be.”
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).