What to Wear
Keep in mind the body in an engine that produces heat. Lots of it. By dressing in layers, you can better regulate your temp and avoid overheating which is the biggest problem for beginners.
Baselayer: A next to skin layer that wicks sweat off the body and dries quickly. It keeps the wearer dry and therefore warm. The best ones are merino wool or synthetic. Cotton is the worst. It absorbs sweat and does not dry. The wearer feels cold, clammy, and wet.
Mid layer: A light sweater, vest, or fleece.
Shell: Jackets and pants made of a “soft shell” material breathe well, offer some water and wind resistance. Insulated or down jackets are most often too hot.
Footwear: All rentals have platform pedals. Any sort of winter boot will work. A pair of Xtra-Tuffs is a fine choice. A trail running shoe will work too, although you don’t want a shoe with lots of vents in lower temps.
15-30 Degrees
Long sleeve wool or polyester base layer. A mid-layer with a zipper so you can vent easily. Finally a breathable wind blocking layer (eg Windstopper fleece, soft shell or goretex jacket) At this temp it is easy to overheat.
Extremities: A very thin stocking hat, mid to heavyweight gloves and wool socks. If wearing SPD shoes, have over-booties and maybe a waterproof sock.
Zero to 15 Degrees
Baselayer, midwieght layer, windproof shell.
Extremities: A balaclava, especially in windy conditions. Mittens or poggios with thin gloves. Wool socks, maybe a thin liner, with insulated boots.
Below Zero
It doesn’t get that cold in Seward very often. No kidding! But when it does, a rider really needs to protect their feet and hands as well as exposed skin. Poggies, or bar mitts, are a must. Insulated winter boots and at least 2 pairs of socks, but never wear boots that are too tight. Insulating leggings with a wind-blocking layer over that. Exposed skin is at risk of frostbite.
Other stuff: Sunglasses with a lot of coverage are really nice to have. Even ski goggles are popular.