130+: Wuss out.

115-130: Shorts, loose white long sleeve mesh jersey, ride slower. Cycling socks. Shoes with lots of mesh.

100-115: Shorts, loose jersey. Cycling socks. Shoes with lots of mesh.

55-100 degrees: shorts and jersey. Skull cap. Cycling socks. Shoes with lots of mesh.

40-55 degrees: long sleeve top, jersey, tights and shorts. Skull cap, ear warmers. Cycling socks. Shoes with lots of mesh.

30-40 degrees: long sleeve top, fleece powerstretch jersey, tights and shorts. Skull cap, ear warmers. Full finger gloves. Cycling socks. Shoes with no mesh.

25-30 degrees: long sleeve top, fleece powerstretch jersey, tights, shorts, legwarmers. Skull cap, ear warmers. Windproof gloves. Wool hiking socks. Shoes with no mesh.

15-25 degrees: long sleeve top, fleece powerstretch jersey, tights, shorts, legwarmers, windproof vest. Balaclava. Windproof gloves. Cycling socks. Shoes with no mesh. Booties.

10-15 degrees: long sleeve top, fleece powerstretch jersey, tights, amfib windproof tights, windproof vest. Balaclava. 2-layer windproof fleece gloves. Wool hiking socks. Shoes with no mesh. Booties.

0-10 degrees: fleece sweater, windproof jacket, tights, amfib windproof tights. Balaclava, ear warmers. 2-layer windproof fleece gloves with liner. Wool hiking socks. Shoes with no mesh. Booties.

-15-0 degrees: long sleeve top, fleece sweater, windproof jacket, tights, amfib windproof tights. Balaclava, ski-mask/heat exchanger, goggles. Down gloves. Wool hiking socks. Shoes with no mesh. Arm and feet chemical warmers stuffed under gloves and booties.

-45 - -15 degrees: long sleeve top, fleece sweater (down sweater near -45), windproof jacket, tights, fleece pants, windproof pants. Balaclava, ski-mask/heat exchanger, ear warmers, goggles. Down gloves (with liner near -45). Wool hiking socks. Shoes with no mesh. Arm and feet chemical warmers stuffed under gloves and booties.

Below -45 F: Wuss out.

But I usually push pretty hard so I warm up. If I'm going a bit slower, bump everything up by 1 layer. Also, this is in the city, where I'll be drafting heat off cars and doing a lot of stop and go (which means the wind isn't continuously sucking heat off my body). It'll usually be a few degrees colder on the open road vs. the city so dress appropriately.