We did cancellation yesterday morning (March 4th) in the 23?F weather. Arrived sometime around 4:50 AM and ended up being 7, 8, and 9th in line. I say "ended up" because there was some shuffling around of the beginning of the line over the course of our wait so it was difficult to know until closer to the time what our position was. Not exactly sure when the first people arrived but it seemed to be in the 3 AM hour, and I overheard that the first person had hired a line sitter for the first couple of hours then switched places. The people in spots 5 & 6 arrived around 4 AM.
About an hour before the show, someone came out and announced that they would be giving out 11 SRO tickets for the matinee and 14 for the evening, so some people in line started doing counts. The first four people claimed 4 mat and 4 eve all together. The next two wanted 3 mat between them. My group of three would have preferred matinee, but that would have claimed 10 of 11 matinee tickets, and the guy behind us wanted two for himself and his fiancee because they had tickets to another show in the evening. He had previously waited for tickets a couple of days ago and been unsuccessful, so in the interest of not screwing him over, we took 3 evening tickets instead.
I cannot emphasize enough how cold it was. We only survived by having brought blankets and actual bedding, including a down comforter, and making an impromptu fort to huddle under. It was toasty enough inside that we felt comfortable taking off our gloves, so I'm gonna do a 10 out of 10 recommendation for down comforters. All this to say, if you're trying to get tickets in the near future, don't assume people won't be out even when the weather isn't great. This is a spring break week for many colleges, and the next couple of weeks are also spring breaks in a lot of areas. (https://www.studentcity.com/when-is-my-spring-break 
If there hadn't been both a matinee and an evening show today, we could easily have been out of luck if they only offered ~7 as they have done in the past, and we arrived before 5 AM.
Side note: Come From Away (across the street) ended up having a pretty sizable line by the time they let people in at 10 AM, but the first person there definitely wasn't there when we arrived and it was very short around 8 AM.
Hamilton Emotional Support Group:
https://www.facebook.com/groups/hamiltonsupport/