My spreadsheet with times and distances for each run also has temperature, windchill/heat index and dew point.  I then have a column for each item of clothing I might wear on a run (tights, pants, shorts, short sleeve tech t, long sleeve tech t, gloves, hat, etc., etc.) and I stick a '1' in the appropriate column for each thing I wear on a given run.  It takes an extra 5 seconds once you've set it up.

Then, on a separate sheet, I have all that data compiled and a spot up at the top where I can enter a given temperature or wind chill.  The spreadsheet searches for all runs that happened within 2 degrees of that temperature (say today is 17 degrees, because it was when I woke up and decided to play basketball rather than run) I enter in that temperature and it looks up all the runs that I've ever done between 15 and 19 degrees and averages what I wore.  Thus, I can see what worked in the past and choose accordingly.  (One this second sheet I adjust some of the numbers from old runs if I noted that I was particularly under or over dressed, so I don't make the same mistakes again.)  After after a couple of fall/winter/spring cycles, I've got data points at almost every conceivable temperature above 10 degrees.  Below 10 degrees the answer is easy: wear everything you own.

C'mon, I thought you guys were running fanatics here?  How can you possibly run without spreadsheets to tell you how you're doing?

cloark, that is FANTASTIC.  I'm geeky enough to do something like that, but I had never thought of it.  I've got a project for Thanksgiving break now.

As for me, today, it was 44 and sunny.  I had a long sleeve tech shirt, loose pants (not tights, some kind of general cotton sports pants I've had for ages), and a ballcap.  I skipped gloves, which was ok, but my hands were definitely cold by the end.  Would have been fine without the gloves for a short run, but I was out there for an hour and 24 minutes.

Sometimes I'll wake up with a weird, inner "chill" in my bones (I have no idea why). Almost as if my body knows and doesn't want to leave the bed  Even if it is only 30-35 degrees, I'll end up wearing tights, thickish socks that rise above the ankle, my thin long sleeve undershirt and one moisture wicking long sleeve over that if I am only running less than 40 minutes because I know I'll barely warm up by the time I am finished. I'll also have something over my ears.

40-30 (unless feeling the chill) - capris, just a t-shirt with gloves if it is closer to 40, or my thin long sleeve undershirt along with a t-shirt and gloves if it is closer to 30.

30-20: tights, thick socks that rise above ankles, long sleeve undershirt, long sleeve moisture wicking shirt, a headband thingy to cover my ears, gloves.

20-10: Same thing for 30-20 but also probably something to cover my mouth and nose, or even a full head mask thingy, possibly thicker gloves and socks that come over my calves.

10 and below: All the above, possibly a windbreaker jacket or something, and last year I wore another pair of pants over my tights when I ran in temps below 0

LRB – Gloves – I have two pair, one light weight underarmour and a cheap cotton that they handed out at the Asheville Biltmore marathon in 2013 when the wind chill was in the single digits.  Neither work in really cold weather and I usually pull my fingers  out of the finger holes into a fist to keep warm.

Arm warmers – how are they better than just a long sleeve shirt (other than, yea, them shits look fly?)

DtotheT – your breakout is what I want to get to.  Had that down pat in my head last year, wish I had written it down.

Cyberic – don’t think I’ve ever run in a Jacket.  (One exception being the marathon mentioned above).  If memory serves me correctly, my normal run layering max is three – base is a medium weight smart wool, next a long sleeve t (either tech or cotton) and last a short sleeve cotton.

Cloark – looks like Eric has taken care of that for us now.  Didn’t realize you could sort/search on temp range.  (thanks AKTrail).  Problem is, I didn’t make notes last year, and the auto temp feature wasn’t in place most of last winter and I didn’t input that data.

AKTrail – see above.  And yes, angle of sun makes a big difference.  Fortunately I do most of my runs at lunch time so what sun there is is mostly overhead.  So a sunny day 35 is a good 5 to 10 degrees “feel like” over a cloudy 35.

Arm warmers – how are they better than just a long sleeve shirt (other than, yea, them shits look fly?)

Heat is my number one limiting factor so it has more to do with that than anything.

Where racing is concerned, I get extremely hot despite the fact that I may be running in 32 degrees F. I am sure there is some coefficient value pertaining to heat generated and its effect on pace and all of that jazz but simply put, having my shoulders and outer chest exposed provides just that little extra cooling where wearing a long sleeve top might have me on fire.

Arm warmers let your arm pits breathe. 

I like them because you can push them down if you get too warm.

I agree there is a hardening off period in the fall, while your body acclimates to the cold.  It's been a really warm, sunny fall in California, and most of my runs over the last month have been high 60s/low 70s  and sunny.    Today is was  in the 50s, overcast with a light wind.  I wore a tank and shorts and was surprised at how cold I was, especially my hands,  the first few miles.  Even by the end, I really wasn't warm.  I felt like such a wimp.

low 30's this AM -- long sleeve tech, thin tee, another long sleeve, tech half zip windbreaker.  Tuque, wool gloves.  Lined wind pants.  For recovery pace, perfect.  Would have been way hot for a quality run though.