I have three horses and blanketed all of them last weekend. One of my horses is 20 and has some arthritis. She gets blanketed if the temp falls below 30. The other two get blanketed if the temp falls 22 or below. During this last cold spell, all 3 were blanketed until mid-week. I had a blanketing discussion with my vet when I lived in a different state and he said its not the cold, it's the wind that can affect them. I keep that in mind also. There was also an article in a recent Equus magazine.