When the weather takes a dramatic cold turn, I feed an evening warm bran mash with a dash of electrolyte salts to help prevent a chance of weather induced colic. In fact, my vet sends emails when the weather turns requesting his clients do this to cut down on all the colic calls he gets on impaction colics when the weather turns suddenly.
Here in Florida we can have 70 degrees one day, then rain, rain, rain, and cold winds come in with a drop to 32 degrees and under. Its the cold winds blowing on wet horses that bothers me, but they will stand out in the weather when they have a chance to be under. I do close in my old mare even tho she does not like to be in a stall. We have a few hard freezes each year and it is a pain, so I feel for all of you having to deal with it more often. I don't have bucket heaters and have to break ice and haul hot water so they hopefully will drink.
In 1989 we had quite a large snowfall and ice everywhere, other years we have had light snow but that was the biggie. I had 3 horses just back from a show, clipped, but plenty of blankets and wrapped legs, they were fine.