Albert Barnes Commentary Matthew 16:2-3

"But he answered and said unto them, When it is evening, ye say, [It will be] fair weather: for the heaven is red. And in the morning, [It will be] foul weather to-day: for the heaven is red and lowering. Ye know how to discern the face of the heaven; but ye cannot [discern] the signs of the times." — Matthew 16:2-3 (ASV)

He answered, etc. The meaning of this answer is: There are certain indications by which you judge the weather. In the evening, you think you can predict the weather tomorrow. You have evidence in the redness of the sky by which you judge. So, there are sufficient indications by which you should judge concerning me and these times. My miracles and the state of affairs in Judea are an indication by which you should judge these times.

Is red. Almost all nations have observed this as an indication of the weather.

In the morning—the sky is red and lowering. That is, there are threatening clouds in the sky, which are made red by the rays of the rising sun. This, in Judea, was a sign of a storm. In other places, however, the signs of a storm may be different.

The face of the sky. The appearance of the sky.