How do the conditions in the plants become even more dangerous over the winter months?

From the text;

"There was no heat upon the killing beds; the men might exactly as well have worked out of doors all winter. For that matter, there was very little heat anywhere in the building, except in the cooking rooms and such places--and it was the men who worked in these who ran the most risk of all, because whenever they had to pass to another room they had to go through ice-cold corridors, and sometimes with nothing on above the waist except a sleeveless undershirt. On the killing beds you were apt to be covered with blood, and it would freeze solid; if you leaned against a pillar, you would freeze to that, and if you put your hand upon the blade of your knife, you would run a chance of leaving your skin on it. The men would tie up their feet in newspapers and old sacks, and these would be soaked in blood and frozen, and then soaked again, and so on, until by nighttime a man would be walking on great lumps the size of the feet of an elephant. Now and then, when the bosses were not looking, you would see them plunging their feet and ankles into the steaming hot carcass of the steer, or darting across the room to the hot-water jets. The cruelest thing of all was that nearly all of them--all of those who used knives--were unable to wear gloves, and their arms would be white with frost and their hands would grow numb, and then of course there would be accidents. Also the air would be full of steam,from the hot water and the hot blood, so that you could not see five feet before you; and then, with men rushing about at the speed they kept upon the killing beds, and all with butcher knives, like razors, in their hands-- well, it was to be counted as a wonder that there were not more men slaughtered than cattle."