Its 14 degrees but absolutely chucking it down. She's an irish draught x TB. She's not clipped.
No. A horse prefers the rain above the sun. Our horse can walk in and out there stables if they want. It's a nice temperature in there. (its made with isolation between the plates). And they will stand outside in the rain, even when there is a storm. But as soon there is a Little bit of sun and there are flies they stand in the stable. Underneath a blanket they heating up their temperature for getting rid of the rain on their back. But the Warmth can't escape completely, and the water can't go away, cause above it's water prove so it can't go trough it. So putting a blanket on when they are already wet in the rain, with a temperature of this will make them only sick. and if it gets to bad, than you can put them inside in the stable. But Absolutely NO blanket cause they start to sweat for getting the water of them (imagine you being wet. And then putting a vest on, it won't be nice for you, and eventually you will sweat also...)
It is warm but just throw a lightweight on to keep her dry. It's just nicer for them to have a bit of protection from this horrid rain. My gypsy cob and my tb have lightweights on and they're not too hot. It's tricky this time of yr!
Horses LOVE that temperature. In fact that is right in the middle of their favorite temperature range. As long as the horse is used to being outside and wet, then leave her.
What is she used to? My TB X Hanoverian is currently in the field with no rug on...I'm in North West England... and she's fine. But she's used to having no rug on, so it depends.
Generally best without rugs. 14 is quite warm enough for her to go about starkers. The major problem is freezing rain, and we're quite past that now if you're where I think you are. (For those stuck in the US where the only temperatures are Fahrenheit, 14C is like 57F.)