Blanketing charts can get ridiculously complicated, and seem to work best when every horse has the same temperature ranges, and the number of blankets is limited. The best I’ve been at wanted 3 blankets only and they had to be turnouts. We used color coded tags on the chest.
OP I’m also in MA and also have a Morgan mare, but mine most definitely is not a yak in the winter; her body gets a bit plushy and she gets feathers on her legs, and grows impressive amounts of hair along her jawline, but that’s it. She had only required clipping when in full work, and then just her chest and the underside of her neck. For this reason, I tended to want her blanketed fairly heavily.
A few years ago, she started to panic about static electricity. She’s normally easy as pie, but blanketing (especially unblanketing) was becoming a real challenge, so I finally told the barn workers to just leave her unblanketed except when it was going to be rainy and/or very windy, or high temp below 25-30 F. And she was perfectly fine! Her 0g is a Rambo Supreme, and it’s black so it absorbs a lot of heat. She was good in that on sunny days down to 20 or so. Some of my barn mates thought I was mean to want her unblanketed on a clear, quiet 45 degree day! (They tended to be the same ones who’d want their horse in a heavy at that temperature!)
She’s out 24/7 now with a shed, so this winter may be different. BO hasn’t started blanketing at all, but the nights are dipping into the upper 30s, so it may be time. Mare is also older now, so she may need more blankets. BO feeds extra hay on cold nights.
