Jamieson, Fausset and Brown on Jeremiah 15:8

8. Their widows--My people's (Jr 15:7).

have brought--prophetical past: I will bring.

mother of the young men--"mother" is collective; after the "widows," He naturally mentions bereavement of their sons ("young men"), brought on the "mothers" by "the spoiler"; it was owing to the number of men slain that the "widows" were so many [Calvin]. Others take "mother," as in 2Sa 20:19, of Jerusalem, the metropolis; "I have brought on them, against the 'mother,' a young spoiler," namely, Nebuchadnezzar, sent by his father, Nabopolassar, to repulse the Egyptian invaders (2Ki 23:29; 24:1), and occupy Judea. But Jr 15:7 shows the future, not the past, is referred to; and "widows" being literal, "mother" is probably so, too.

at noonday--the hottest part of the day, when military operations were usually suspended; thus it means unexpectedly, answering to the parallel, "suddenly"; openly, as others explain it, will not suit the parallelism (compare Psa 91:6).

it--English Version seems to understand by "it" the mother city, and by "him" the "spoiler"; thus "it" will be parallel to "city." Rather, "I will cause to fall upon them (the 'mothers' about to be bereft of their sons) suddenly anguish and terrors."

the city--rather, from a root "heat," anguish, or consternation. So the Septuagint.