autumn/winter and maybe a flyrug in summer to stop greu horses getting cancer and stop them getting bitten!
it depends on the weather,season, and the kind of blanket
Winter I should imagine.
winter
There are two answers to your questions:If you are asking "if you need a blanket under a saddle" then, yes. It is to protect a horses back.But, if you are asking "if you need a full body blanket to keep a horse warm" then, no. Unless you are in Norway and you have a very thin coated horse.
If you blanket a horse at the beginning of Autumn then it has to stay on until warmer weather comes around again as the blanket prevents the horse from growing it's winter coat. Without the the natural hair coat or the blanket the horse could become susceptible to influenza. You can also blanket a horse with a thin blanket in the summer. This keeps the flies away and prevents the horses coat bleaching in the sun.
winter and fall but mostly winter
Winter
Usually you'd get your horse a new blanket in late fall or early winter. Or what ever the coldest season for your region is.
The answer is pretty simple... WINTER!Winter
Winter
water blanket and food so he/or she can stay warm and be not starving
Horses typically need blankets during colder seasons, such as fall and winter, when temperatures drop below their comfort level. Blankets help keep them warm and maintain their body temperature. It's important to monitor the weather and your horse's condition to determine when a blanket is necessary.