Somewhat as a follow-up to my previous post, the weather yesterday started at 40 degrees at 6am and had moved to 41 degrees at 8:45am. My first inclination was to set up the trainer in the kitchen, but the wind was calm and the sun was out. Certainly it had to warm up soon. Anyhow, I put on my shorts and tights, a long-sleeve cotton shirt under my bike jersey, and slightly heavier socks. By 9:15 I walked outside to mount up. It felt much warmer than 41 so I checked and sure enough the temperature had risen to 48. Okay, I knew I had over-dressed, so went back in and removed the long sleeve shirt, switched to a wind vest over the jersey because I wanted two layers on my chest and arm warmers, kept the tights on. The 30 mile ride had no real challenges and turned out to be quite pleasant. After 30 minutes I lowered the arm warmers, but the wind had come up so the vest stayed in place, as did the tights. It didn't get warm until a few miles from home, so I saw no reason to stop to remove anything. The temperature when I got home was 58 degrees. Once again I guessed correctly on what to wear. Of course, like any layering action, had the temperature risen more rapidly, the outer clothing could have come off earlier.
The second point about colder weather is hydration. Yes, you cut back on how much you drink, but you still need to stay hydrated. For instance, in normal summer heat (under 90 degrees) I drink two 24 ounce bottles on this ride; in hot,humid heat I switch to a Camelbak with about 70 ounces; but in the cool, dry weather like yesterday, I only consumed 30-32 ounces. My time was also about ten minutes quicker than normal, so that might account for a few ounces less. My point is: take the same amount of liquid with you on your rides until you find out how much less you really need. It may surprise you that it is only a few ounces.