I too have seen Amish in northern Minnesota going home in their buggies at-26 not including the wind chill with as my wife commented nothing more than horse farts for heat. However, I have also seen three Amish men fishing in a small rowboat with their horse tied to a tree in the shade at the side of the lake. I had to admire the peace and simplicity of their fishing trip.
Depending on what their church district allows, those buggies have battery operated heaters in them.
They can also heat bricks and take them along.
One very strict group in Ohio does not allow ‘topped’ buggies, which means the people are in the open regardless of the weather.
There are dozens of people who make their living driving the Amish. Their white 15 passenger vans are too numerous to count in Holmes county OH. They are quite busy when it’s cold.