JMNT(i)
2 So, giving a decided response, He said to them," [note: from here through vs. 3 is omitted by Aleph, B and others] Upon the coming of evening, you folks are customarily saying,' [It will be] fair weather (or: good weather; a fine day), you see, the sky continues being fiery-red;'
3 "and early in the morning, [you say], 'Today [it will be] stormy (or: rainy; or: wintry weather), for the sky continues being fiery-red [and] is progressively being gloomy-looking.' On the one hand you, by experience and familiarity, habitually know how to read and discern (thoroughly discern, judge and decide about) the face and appearance of the sky, yet on the other hand, you continue unable and without power [to discern and interpret] the signs of the appointed seasons and fitting situations (or: fertile moments)!
4 "A worthless, wicked and adulterous (or: immoral; [note: an OT word and figure for Israel's idolatry, e.g. Ezk. 16:32]) generation is habitually searching for and thoroughly seeking a sign, and yet a sign will not proceed in being given to it, except the sign of Jonah!" Then He went away, leaving them down behind (or: it may = Then turning His back on them, He walked away).