When I lived in Michigan, I used a Giant aero road helmet, with the vents taped over with electrical tape, for winter riding. I also got some fleece fabric (scrap from some neck gaitors I made) to cover the V shaped hole your ear sits in between the front and rear straps. Basically I made a little taco shell that fit around the V, and safety pinned it through the rear strap. It covered my ears enough that I didn’t need an ear cover or hat.
I personally can’t stand the feeling of a tight fitting hat holding my ears against my head. For whatever reason, it gives me a headache, especially while riding. Thus, the helmet that integrated in the ear covers was awesome, because it knocked the wind down enough, but didn’t push in on my ears too hard. For reference, I was able to use that helmet, sans hat or ear covers, in Fat Bike races down to about 0F, and while road riding down to about 15F.