In our neck of the woods the people who own horses put jackets on them when it gets around 45 degrees F. Horses are outside animals and are presumably used to outside temperatures, so why would they need jackets? Also, if it makes a difference, these aren’t prize-winning animals, just everyday horses.
I am not a horse person but used to have a girlfriend who was. They are “blankets.” There is some degree of controversy about when and whether horses should be blanketed. Here is one opinion that you give you the flavor of the discussion. Some horse owners do it as a matter of course and some try to avoid it as much as possible. I suspect that at least a few horse owners who use them are anthropomorphizing the animals, but probably not as badly as poodle owners :).
(Another similar controversy is whether to feed them corn.)
Just because they’re outdoor animals doesn’t necessarily mean they’re used to the cold. Do horses come from a warmer climate originally?
Most horses can adapt to almost any weather and suffer less from the cold than people do. I have known horses to go comfortably unblanketed through a Minnesota winter. However, many people clip their horses’ coat in the winter so they won’t be soaked in sweat when they work. Sweaty horses must be slowwwwly cooled off until the coat has dried completely which takes a long time. Even for people who don’t clip, blanketing prevents the horse from growing a thick winter coat which cuts down on cool-down time. A small percent of horses idiosyncratically won’t grow a heavy coat no matter what and require a blanket.
Once you’ve made the decision to blanket, you must continue to do so all winter.
Horse require shelter from the rain; some horses that aren’t blanketed with heavy winter blankets, sometimes wear a “rain sheet” which is just literally a waterproof cover with no insulation that keeps the rain off. By law horses must have a natural or artificial shelter (thick trees or a 3-sided shed) but some horses just stubbornly stand in the rain like idiots.
Finally, they may not look like “prize show horses” to you (honestly, how would you know?) but owners of even “regular” horses worry about and spoil their horses.
Horses that live in cold climates and are kept outdoors are perfectly capable of growing their own fur coats and surviving outdoors. But horses kept in stables and used in competitions (racing, dressage, eventing, etc.) usually have their coats clipped or shaved. This is because in heavy exercise the horse will sweat, soaking the coat. If then left to the outdoor temperatures, the wet coat will cause the horse to become chilled. So the heavy winter coat is removed.
This allows the horse to be ridden or used in heavy exercise, and to sweat normally to cool itself off. The animal is then rinsed or washed to remove the excess sweat. When finished, the short coat dries (often with help from the groom) quickly. The horse is then covered with a sheet or blanket to keep it warm.
Of course this makes for a running joke among equestrians – variations on the theme that we all shave our horses in the winter, contrary to superficial expectation.
ETA-- on preview, thanks Hello Again!
Horses can develop thick coats during winter. Good for keeping them warm, but bad if they’re going to be ridden, as this can overheat them.
So, you “clipper” your horse. Some basic info here: http://www.newrider.com/Library/Horse_Care/clipping_how_much.html; and here: http://www.eques.com.au/general/march2005/cliptips.htm.
Of course, once you’ve clippered off their coat, they’ll need protection, thus the blanket. Some horses aren’t blanketed, but wear a rain slicker. Also, some older horses (arthritic, poor quality coat) need a little more warmth than their natural coat provides.
ETA: ninja’d by Hello Again and CannyDan!
“By about 5 million years ago, the modern Equus had evolved. Equid teeth also evolved from browsing on soft, tropical plants to adapt to browsing of drier plant material, then to grazing of tougher plains grasses. Thus proto-horses changed from leaf-eating forest-dwellers to grass-eating inhabitants of semi-arid regions worldwide, including the steppes of Eurasia and the Great Plains of North America.”
Excerpted from: Horse - Wikipedia
Another reason for clipping is when the horse’s coat hasn’t shed by the time competiton season starts in the spring, or alternatively, when the winter coat grows too fast in the early fall. Horses in competiton are often kept “under lights” to prevent the latter (lights on at least 18 hours) to prevent the early growth as the growth is triggered by the absence of sunlight, not the weather.
The winter coat consists of a dense overcoat plus long “guard hairs” that keep the snow off (snow settling a horse in full winter coat will not melt!). Winter shows are usually more causal affairs in northern climates, and she shaggy-beast look is acceptable. Formal showing means formal grooming and a full clip. High level competitors trailer to more favorable climates in the winter and must look the part with a smooth, gleaming coat.
This image shows a trace clip which is where the hair is clipped only in the areas most likely to sweat, while the hair on the back and legs is left alone. This is the most common clip for practical reasons when a full clip is unecessary. Clipping the horse is BIG job that burns through blades and industrial clippers like you wouldn’t believe. People clipping solely for the cooldown advantage do the minimum necessary.
The last and final reason for blanket is to keep the horse clean when he don’t wanna be clean.
Shedding your coat is ITCHY. What’s good for itches? ROLLING ON THE GROUND. What’s on the ground in spring and fall? MUD. YAAAYYYYY.
If you’re the average horse owner who fits in riding time after work and on the weekends, the first time you take an hour grooming off a caked-on 1/4inch thick layer of mud so you can ride, it will be your last. 
Pretty soon there will a rain sheet on the stall door with a note: Sheet if muddy.
I sometimes wear my jacket even when it’s too hot as it’s too much hassle to take my keys, phone, wallet + everything else I need out. I imagine the horses have got a simlir thing going on.
Thanks for your replies! Horses seem like they are much more work than I first thought.
There is indeed an awful lot of work, but my wife claims the satisfaction exceeds the effort. I don’t ride, I just facilitate, so my perspective is perhaps skewed.
But one thing I am certain of-- I used to own boats and I was sure they were the fastest path to bankruptcy. Now we have horses. Plural. So I can say with considerable authority that boats don’t hold a candle to horses in the expense department.
I blanket some of my horses, but not all. I blanket the one I ride, because he is clipped, and the no-mud thing is a bonus too.
I also blanket 3 of my retirees who are in their 20s and 30s, because they can’t eat enough to keep warm and they start losing weight. That internal furnace requires roughage and calories, and becomes less efficient as they age. Frankly, I go through a lot less feed if I keep the old farts blanketed. The two ponies and the pseudo-mustang stay fat as ticks on air, and grow incredible coats so they get to stay nekkid.
And yes, they are a LOT of work, even when not put in stalls (mine live out w/ run-in sheds). This time of year the temps fluctuate so much here in TN that I am forever checking the weather site and doing the ‘blankets on/blankets off’ dance. Cooking them inder too much blanket isn’t any better for them than freezing them, alas.
Blanketing a horse compresses the natural loft in their haircoat so they lose warmth from that insulation which has to be replaced by the blanket. Keeping a horse blanketed requires a lot of attention to make sure they warm enough but not too warm which can end up costing the owner a lot of money in horse clothing of various weights.
One situation in which horses can become dangerously cold is when they are soaked and the temperature drops/the wind picks up. A sheet (a lighter version of a blanket) can keep them dry and cozy, but again needs to be warm enough to make up for their natural insulation at that time of the year. Wet blankets offer no protection so waterproof blankets called turnouts are also used.
Keeping a horse blanketed also involves keeping them clean and making sure they fit well so that the horse doesn’t get rubs or abrasions. The fasteners must also be adjusted correctly and maintained so that the horse doesn’t get tangled up and hurt. Horses are really good at getting hurt and yes, zombiemommy they can manage to be a whole lot of work. But “the outside of a horse is good for the inside of a man.” : - )
Just to add to what has already been said… many horses grow enough coat to stay warm through the winter and don’t need to be blanketed, but some horses just don’t grow a lot of coat. My Thoroughbred was one - maybe he was just naturally thin coated or maybe he spent too many winters in Florida when he raced, but it seemed to make him happier and keep weight on him better if he was blanketed in the winter. Plus all the benefits others mentioned like being able to clip the areas that he sweated most making cooling him out after riding easier and not having to give him a ton of grain so he didn’t look like a walking skeleton.
I forget who it was who said the best simulation of yachting was standing in a cold shower tearing up hundred-dollar bills.
And one more thing – you should always make sure the horse is under control before you put on or take off a blanket. If the horse took off before the fasteners were properly adjusted it could easily get hurt or even killed.
I made this mistake with my horse one day. She was a very athletic thoroughbred mare off the track but very quiet and cooperative for the most part. One warm sunshine-y winter day I went out to check to see if she was getting too hot and indeed she was sweating under her blanket. No need to go to the effort to go back for her halter and leadrope because I was confident she would stand still for me to take it off.
There is a particular order considered the safest for removing a blanket and I followed it. First I undid the elastic straps that went around her legs and clipped back to D-rings on the sides of the blanket. Then I undid the metal tabs that fastened the belly straps criss-crossing from side to side under her. Some horses will allow you to pull the blanket over their head instead of unbuckling the front (if you are careful not to cause them to get static shocked) and mine was okay with it so I gathered it up and started to slide it up her neck and over her head.
This is when things went wrong. Even before her head had completely emerged she decided she was so happy to be free of the blanket she took off for an excited tear around the pasture. Unfortunately one of the small but heavy metal snaps on the elastic leg strap caught in her tail as she ripped away at approximately Warp 8.
As the horse got farther away and the elastic stretched impossibly I stood there holding the blanket, knowing I needed to do something but not having time to really process the situation. Things slowed down, the sound of her hoofbeats began to fade, a feeling of impending doom began to form, and then … the snap pulled free. I saw the glint of it, a weighty metal projectile rocketing back. Directly. At. Me.
Before I could act on a fleeting and half-formed instinct to throw down the blanket and run away, it struck me directly in the center of my forehead. The force nearly knocked me down, and I was so dazed it took me a few minutes to figure out the who/what/where. An egg-sized lump formed before I managed to stagger all the way back to the barn and lasted for weeks as a reminder that stupid should hurt.
Wow! Not only do they have what i referred to as jackets, they have a whole wardrobe! So, if they are this much work, why do people have them? (please don’t pelt me with rotten fruit, I’m not saying horses aren’t nice animals, but I truly don’t know what’s the payoff for all that work, or maybe there isn’t one)
Originally horses were kept for work and for transport, because there was no alternative. That’s why for example, Drais invention of a running machine became a breakthrough during a cold and wet summer when hay prices skyrocketed, making horses even more expensive than before. Then cars came along, that didn’t require constant feeding and care, and horses died out, leaving only the sport side (racing, jumping, dressage), where horses are like other expensive sport machines, and recreation - because for many people it’s a pleasure to ride horses on a nice morning. They’re like yachts or expensive mountain bikes in that regard - some sports require more expensive equipment than others, but that doesn’t translate into more or less enjoyment, just that people’s tastes are different.
I have them because I like them, and their company, despite all the work. I love to ride and to show, but I’d have horses even if I couldn’t do those things.
I basically prefer the company of animals to that of people, which is why I have 18 animals, 1 husband, and no kids.
Come to think of it, this:
applies to kids more than horses in my mind! 