Ok,, here's a decent case study.
Yesterday we had 2-3 inches of snow that dribbled down over a period of about 6 hours. Temps were low 30s, nto quite neough to keep it melting. The result was that if there was much traffic it packed into a thin layer of something very close to ice.
By 7 this morning it was down to 5 deg. F, with some sunshine thorugh broken clouds and a 5-10 mph WNW wind.
A friend of mine operates an equipment sales and rental shop near me. Over the years he has done his share of favors for me. By way of thanks, I make a habit of salting his lot if I have some left int he spreader after I finish my run. He had plowed late yesterday afternoon, after the storm had passed. The yard was covered with a layer of pack, well tracked down from traffic.
I dropped 3-400 lbs on an area that I would consider to be around 15,000 sq. ft. then headed home for sleep. I stopped back this afternoon with a question and he asked what I had put down. This fellow has been involved in large sacle commercial snow operations in the past so he knows a bit about what's "normal". He commented that he knew it was too cold for salt to work, and that he was amazed at how fast it burned the pack off. His other comment was that he thought, at first, that it was sand from the color and that it didn't look like I put down all that much.
Anyhow, I dropped close to 4 tons last night, more than I would normally apply, but due to the low temperatures I felt it was better to overapply and clean things up. Virtually everything was bare and black by early afternoon.