I think I’ve finally hit on a combo I like for running in dry, not too windy conditions between 20-40 degrees Fahrenheit. This is a mix of stuff I’ve had in my closet (fleece tops from Christmases past, a summer running tank, a spring/fall running long sleeve) and a couple extras I had to get for colder conditions (breathable gloves, something to cover my ears).
Base layer: My favorite running bra; a long, sweat-wicking tank top; sweat-wicking running tights; Balaga socks; running shoes with enough tread to handle patches of snow.
A little extra warmth layer: A wicking, long-sleeved running shirt (preferably with thumb holes to keep the sleeves down over my wrists); baggy athletic pants (you know, the generic kind with the three stripes down the side).
Toasting toppings layer: A lightweight, long-sleeved fleece with a collar.
Warm accessories: Gloves that keep my hands warm but don’t get soggy with sweat (I got the Under Armour variety from Scheel’s on Saturday); a baseball-style running hat; a headband with a fleecy interior to cover my ears that still fits over my hat. A beanie with a brim could probably substitute for the hat plus ear warmers.
Gadgetry: An iFitness belt so I can easily carry my phone — which has pretty much replaced my Garmin thanks to the RunKeeper Pro app — and some chapstick.
If I got overheated in any of that stuff, it would have been pretty easy to peel off one layer at a time and tie it around my waist. I get cold easier than I overheat, so on my long run on Sunday I felt fine the whole time in that get-up, especially considering that all my technical base layers wicked the sweat away before it could make my clothes soggy and cold. It was in the low 30s.
If you do overheat, and you do loops, you could always drop each layer off at your point of origin (e.g. your car, your house) and it will be waiting there for you when you’re finished with all your laps.
If it was colder, windier, or wetter, I’d probably want to get a full-on balaclava (you know, like what bank robbers wear — keeps your face from going numb) and some wind- and water-proof pants and jacket, and substitute the the baggy athletic pants with a heavy pair of sweats that are nice and fleecy inside. You can also find warmer base layers than tights and a tank top if it routinely drops below 20 degrees where you live.
Of course, there’s always the treadmill! All you need are shorts and a t-shirt all year long.
Stay warm, friends!