my guess would be that the areas not near water, or the ocean effect, would drop about 15 to 20 degrees a day, until it reached what the polar regions are when there is no sun----that is, to about minus 50 to minus 80 F.
As soon as the oceans cool, that's when every thing would definitely drop even lower. And with no sun, the plants would die off---I can't remember who determined exactly as to how fast after the meteorite hit that most of the vegetation died off, but I'd guess a week to three weeks, and it wouldn't help the plants as the temp drops below zero everywhere--end result: no new food production or oxygen production.
So besides the suicides, murders over food, riots, the temps so cold, no natural light to get around, etc. --I'd say 90% of the population gone within two months-95% gone in six months-99.99999% gone within a year---the rest gone within two to three years, except maybe some, 5000-10000, within some governments with highly specialized long term shelters.