Albert Barnes Commentary Luke 12:55

"And when [ye see] a south wind blowing, ye say, There will be a scorching heat; and it cometh to pass." — Luke 12:55 (ASV)

South wind. To the south and southwest of Judea were situated Arabia, Egypt, and Ethiopia, all warm or hot regions, and consequently the air that came from those directions was greatly heated.

How is it that ye do not discern this time? You see a cloud rise, and predict a shower; a south wind, and expect heat. These are regular events. So you see my miracles; you hear my preaching; you have the predictions about me in the prophets; why do you not, in the same way, infer that this is the time when the Messiah should appear?