V 11, 12.
At that time this people and Jerusalem shall be told:

Quest Study Bible notes, p 1044.  Before the fall of Jerusalem, some people may have responded to Jeremiah's message, but the sin and hard heartedness of the rest of the people no doubt remained.  So Jeremiah continued to warn about coming judgement.
Even today, a hot, dry southeasterly wind can blow across Palestine for three days to two weeks.  fine dust fills thye air, making life extrememly trying for both humans and vegetation.  A normal wind can blow away chaff, to winnow or cleanse, helping the harvesting process.  But this hot wind destroyed the crops.  For Jeremiah, this natural phenomenon was a metaphor for the fierceness of God's judgement.

This is a good description of a people who ignored God and thought they had it all together without him.  How many people do I know who are like this?   Jeremiah describes them as 'foolish' and like 'senseless children' - silly little children.  As a kindergarten teacher I can relate to this description.  Some children - and teenagers, too - are full of self confidence - misplaced confidence.  They think they can do anything.  They think nothing bad will happen to them.  They think they know it all. when adults continue to think like this they are very foolish.  Even Christians sometimes forget to be guided by God.  How often do we barge on, making our own decisions and forgetting to consult God or to try to discover his will for us.  It is only when things go wrong that we come to him for help.

V 23 - 26

Jeremiah's vision was of total disaster over all the earth. This must be the picture wherever devastation and disaster strike: in war zones and natural disasters.

New Bible Commentary, p 678.  Judah's convenant failure does indeed affet the whole world.  Jeremiah now pictures nothing less than an undoing of the created order of the world, in words stikingly like those of Genesis 1: 23-26.  If the covenant with God's chosen people were to fail there could be no hope for the world.  That is why Christ's life must be seen as a fulfilling of that covenant, in order to be a light to the Gentiles (as prophesied in Isaiah 42: 6)

V 27.

God is a merciful God.  Though he has the power and the right to destroy the whole earth when the people are totally disobedient to him, he does not do this.  There is always hope.  Our hope is in Christ. (see Commentary note above).  Without Jesus, we have nothing.  With him, we have everything to hope for; strength and comfort in time of trouble, a life of satisfaction in serving him, a future in eternity.

V 28.

Quest Study Bible note, p. 1045.  Apparently, by the time this oracle was spoken, the time for repentance had run out.  Some speculate that this section, or at least large portions of it, were spoken just before the fall of Jerusalem.  In terms of just Jeremiah's ministry - not to mention the other prophets - Judah had had at least 40 years of warning.

God did not change his mind about the future of Judah.  They had had many years of warning but had ignored it.  God had made his will very clear through his prophets.  So the time had come for judgement. The time of judgement comes eventually to each one of us, even those of us who have accepted Christ and are forgiven.

I read once a story about a person who entered heaven and stood before God for judgement. (I'm not absolutely clear on the details and I wish I could remember where I read it! I think this is how it went....)  The person had not led a very 'good' life.  As God read through the book that re-told the person's life and actions, nothing was said. Page after page was turned, each one describing some deed or thought that the person was ashamed of.  God made no comment, just read.  The person became more and more ashamed. At last he came to a page which recorded one action of goodness and God looked up and smiled at the person in front of him. Somehow - can't remember this detail of the story - the person before God became aware that as the pages of the book were read, each one with the bad things were wiped off,  but the page with the good record remained recorded.  Because in life that person had accepted Christ, so was forgiven.