To blanket or not to blanket, that is the question. And oh boy do people have some serious debate over it! It can get overwhelming for new donkey owners.
Do you know what the simple answer is? It depends on your animal and your situation!
Older donkeys, donkeys with fine coats, donkeys who are thin or ill, donkeys who are suddenly thrust into harsh weather after a spell of warm weather, donkeys who do not have adequate shelter, or who refuse to use their shelter during storms....all of these may require a well fitted blanket.
Donkeys, unlike horses, do not have two layers of fur. Therefore, water simply soaks into their coat after a while and end up on the skin. They do not slick off water well. The worst days I have found in CO are the 40 degree slush/snow mix days. Donkeys are not built for wet weather, they are desert animals.
If you live in Florida, you likely would only need a blanket in case of illness or very wet weather. If you live in Canada, you likely will want one just for the extreme cold and snow.
Don't think that any old winter horse or pony or mini blanket will fit a donkey. Donkeys have different proportions than horses and the neck area especially tends to be problematic. Horse blankets are made with very sloping shoulders, and often end up sliding back on a donkey and getting stuck behind the winter area, causing extreme pain and rubbing over time on the shoulders and back. I have found Weatherbeetas especially good for my mammoths, but there are other companies that make smaller, very adjustable blankets that work well for other sizes of donkeys. Donkeys usually need blankets with very little "fill", they need it more for the waterproofing quality of the blanket. But an older, thin, or ill donkey may need a warmer blanket of course.
Another way to help keep your donkey warm is to make sure they can eat many small meals throughout the day and night, the stemmier the hay the better. The digestive process, especially digesting stemmier forage, creates heat in the gut and therefore warms the donkey. Chewing straw on cold nights can help as well. We go out and feed on nasty nights at around 2 am in addition to regular meals.
Be sure that you have a water tank heater that works when it is very cold out, as drinking water is super important in the cold, and donkeys tend to get discouraged about drinking icy water easily, which can lead to colic.
Even if you don't believe in blanketing donkeys, having a well fitted blanket for each animal on hand is really important. You never know when you might need one. We almost never blanket, but today we did as it was 80 yesterday and today it is freezing and snowing sideways. Even though our donkeys have winter coats, that is quite a sharp change in weather! It is simply kind to help them out. I am glad we had our blankets on hand and ready!
So the moral to this story is: Decide on your own. Be ready and have one. If you feel like they should be blanketed, blanket them. If you think they are doing fine on their own, then don't. Everyone has different situations and may have different needs.