When it comes to cooler weather, there are three things to think about: staying warm, staying dry, and protecting yourself from more treacherous conditions.
Warm isn’t as straightforward as it seems. If you dress too warmly during climbs you tend to sweat. Sweat is water no matter how bad it smells and will soak clothes – including the so-called wicking fabrics. And if you take layers off, unless you have a place to store them, they can become either a hazard, get wet, or lost. We solve the problem by wearing packs that are at least water resistant and always bring a lightweight, waterproof jacket of some sort during the cold winter months. Keep any other extra layers in a plastic bag and they’ll stay dry as well. If you think the temperature may really drop on the way down, think about tossing in some ski gloves and maybe even some toe warmers in that pack. Remember, if you lose feeling in your hands, you’re going to lose the ability to maintain control of your bike.
While staying 100% dry from sweat is a huge challenge, it’s easier to stay comfortable and avoid getting the chills. First up is a good rain jacket. Get one that’s truly, guaranteed, waterproof. Don’t get a thick, heavy, or insulated jacket but rather the thinnest, lightest one you can. You’ll wear and pack it more often and if you need more warmth, layer up underneath; use the jacket to stay dry, and resist the effects of the wind, not to maintain body heat. Also, make sure the jacket has a long tail, specifically for cycling or water and dirt will come off your rear tyre and get in to your shorts and that’s no fun. Oh, and make sure that the jacket arms are also “cycling cut” so you can extend them fully without the jacket material binding anywhere.
Waterproof pants are a good thing to have as well. There again, get material that is truly waterproof and make sure they’re made for biking as hiking, running and other types of clothing may not be reinforced or cut in a way to either last or allow comfortable cycling range of motion. And make sure you have something (like a Velcro strap) to keep that drive side pant leg out of the chain and chain rings!
There are all sorts of special cold and wet weather gear items. Go to your local bike shop and check out everything from Capestorm, First Ascent to waterproof helmet liners to anti-fogging fluids for your eye protection.