Horses, and cattle are plains animals, they prefer cold dry or hot dry climates of grasslands, prairie or steppe landscapes. Your location is ideal for them.Horses that winter outdoors get a very fuzzy look to them with their winter coat...and shed in in clumps kinda like deer do. The sleek look seen in movies is usually summer coat
Damp wet climates are bad for them and they don’t like it. Also hot humid they don’t like. So Ontario is not a good place for horses.
And Donkeys do not grow winter coats like horses do, not do they shed like a horse. They are more desert animals, I have seen donkeys here with missing ears from frostbite. People think they are tough but they are not winter hardy for cold at all. And wet is just horrible for them. Sort of like a silkie chicken they don’t shed water very well at all.
Polish also have a herd time with rain! Silly boy why were you put in that rain?! He had a bad hair day.