A horses winter coat no matter how fluffy will protect them from straight ‘cold’ weather with the correct amount of food and water. It’s when you add in the wind and moisture that horses don’t have much defense against. I live in ND and we spend a lot of time in the below zero range. A few years ago I only blanketed my gelding when bad weather was coming or the windchill was well below zero, otherwise I would just make sure his hay was in his run in shelter and he was perfectly content. Last year and this year so far he has needed much more blanketing. He will be turning 21 this Feb and he starting to show his age when it comes to keeping himself warm. He has had a turnout sheet on since the temps dropped below 50* and now has his medium weight on while our temps are in the 20s. The next step will be his 300g once we get closer to zero or below zero windchill days. He has a schneiders extra heavy weight with a belly band and fleece liner he got last year for those icky icky nights. Basically my point is.. Age plays a big role. We have some horses at my barn who are on 24/7 turnout and are never blanketed, even when it’s 40 below and icky out. They just get their hay in their shelter and they are as happy as can be. Your horse will let you know how he feels. If he seems content with a little extra hay and getting out of the wind rather than a blanket then that’s great! Blanketing is a great option but once you put that blanket on for an extended period of time, you can ruin some of his natural defense against cold so that means you are blanketing all winter and into spring.