A little off topic, but there is an approach that shields hands from wind, (and body from face to upper thigh) and incidentally reduces wind resistance as much as a rider in front - a handlebar fairing. Also keeps you far drier over that same area. I used a Zzipper fairing for years. In Ann Arbor, wow! did it help. I loved it when I did a due south 15 mile commute through Seattle in winter. (Storms there come from the south and were a regular feature. 20-30 mph headwinds with rain were a regular feature of my morning ride. (Ballard to well down the Duamish River via Alaska Way for you Seattleits.)
With the fairing, chopper mitts and wool inner mitts work just fine in any weather Ann Arbor can offer up. Those mittens have been my favorites for years for comfort, ease of on and off (on long rides, pulling then off to reach into pockets is easy. so is putting them back on). They have a huge range of temperature. Pull the inners out and ride just the leather into the 70sF. Keeping them clean inside and smelling nice is also easy.
Ben