Do you think that waistcoats were worn mostly in the Winter and Spring?
I would think so.
Vests were common men's
dress in America year round...
They were frequently put off, along with coats or jackets, when men were at work.
That said, many Southerners in that era, perhaps event the larger number in the deep South, didn't even bother about them even when at leisure. From Lippincott's magazine, 1870...
T.W. Caskey's notes on "Seventy Years in Dixie" recalled that most common southerners didn't bother about them even in church... with the average country preacher dressed for work in the pulpit exactly as he labored in his fields...
But in the Army the men were subjected to exposure in camp and field in winter. It was were advertised in the Southern papers that vests were important for the soldiers in the winter. The notices in the Southern papers in late 1861 called on the women of the States to make up suits including stout vests of jeans or kersey if possible, for winter wear...
The State of North Carolina, among others, subsequently labored to produce suitable "winter clothing" for the Confederate troops...
However, the Confederate Army's "commutation" funds for soldier's clothing was based on the cost of the regulation uniform of the CS Army, which did not include vests. So where vests were provided, they were not recognized as "army clothing" for the purposes of commutation payments to the States, etc. providing clothing. But we see they were widely worn by the troops from wherever procured.
George W. Maddox of the 18th Georgia wrote home in November, 1861 for winter clothing, including a vest, besides what was allowed for by the Confederate commutation..."Woolen clothing is out of reason and I would like for you to have made me a coat and pair of pants and vest made and sent to me with those coats belonging to the Confederacy Shields has my measure, tell him to cut the coat a little larger than the measure, say about 2 inches around. Have Georgia buttons on coat and vest and send me the receipt of his whole and I will pay it…"
Reuben Pierson of the 9th Louisiana noted in late 1861 to his father that he required a good double-breasted jeans vest, "it will be of more service to me than any other garment in this cold climate where the mornings look very much like it would frost..."
Some Confederate prisoners taken at Woodstock, Virginia in 1862...
In summer campaigns, the Confederates, where they could, often made due with "summer clothing" of a lighter weight... which was generally procured from home, and was more akin the common working dress, and frequently without even a vest. William Watson of the 3rd Louisiana recalled this generally included overshirts or "tunics" of figured or hickory calico, etc.
....
Moxley Sorrell of Gen. Longstreet's staff, noted at Chickamauga the troops of Bragg's army were not particularly uniformed, but many made use of these "western tunics" in lieu of any other outer garments, to great advantage in the hot weather, etc.
... and in the field in the summers frequently, if not generally, the troops often dressed down in the hot weather...
Lee's Army in June, 1863...
Looking at the images of Confederate dead at Gettysburg, most are wearing jackets without vests...or just shirts, but here's one unfortunate who appears to have been wearing just a vest...
Walker's Texas Division in mid-1864...
Hoods' army in late 1864...
Bringing the