I've gone through this dilemma many times. I just ran a half in Massachusetts just a few weeks ago, and even then, it was very cold and windy. I found that when I get "in the zone" and running, I can go in a sleeveless shirt and shorts.  However, that isn't everybody. I think the safest thing to wear would be a long-sleeve t-shirt, shorts, and compression shorts. Maybe that's not the safest, but most neutral uniform.  Just keep trying new things at the same temp you're going to be running the race in, like long spandex, running pants, jackets, or even shorts and a t-shirt, etc. and find what's best for you as well as what's most comfortable for your body.

Try a plastic Garbage Bag with 3 holes cut into it for your head and arms. It's cheap, disposable, and it does the job EXTREMELY well.

y'all are nuts! i'm freezing constantly anyway, so i wind up wearing those cheap cotton gloves ALL DAY - at work, at home, to bed..

as far as cold weather races or just running in cold weather.. i recently ran a 5.5 mile race and it was cold. not freezing - i was freezing, but the weather wasn't actually at 32 degrees - and there were crazy people out there in sports bras and shorts! most people wore shorts and t-shirts, but me? when it's cold, i run in: ear muffs, running gloves, running tights, knee high leg warmers, shorts over the tights, running pants over those if it's really cold, a long sleeved running shirt, a tank top under that if it's super cold, and a thick running jacket i got at victoria's secret. and i'm still freezing! i don't warm up till almost mile 2, and then god forbid i stop running for even a second; i immediately freeze. i add a scarf if it's windy, cause my nose feels like it's going to fall off.

but.. as cold as i am, i would MUCH prefer to run in the cold weather than in the heat. i hate sweating to death way more than i dislike being uncomfortably cold.

That just shows how different people are.  I have lined up for the Marine Corps Marathon at 45 degrees several times in shorts and singlet.  I'll wear something throw-away to keep warm before the start.  Of course at the finish it will be 60 - 65.  I always wear a hat and at that temp I'll have a pair of light gloves for the first few miles.  For a shorter race I might wear more, maybe a long-sleeve shirt and compression shorts under my running shorts.  As it gets colder I'll go to full length tights and a short-sleeve shirt over the long-sleeve one, or a windbreaker jacket if it's windy.

Len

45 degrees I wouldn't even bother changing much from my summer gear,  maybe go long sleeves and those longer shorts that go just past the knee.  Does anyone use Under Armour? I was wondering if I should wear a tank top under it or over it or will laying matter at all?  

I am a huge wimp about cold, so I'm usually pretty impressed with myself when I get a run in under 50 degrees!  My Thanksgiving Day 5K was just over 32 at race time and I thought I was going to FREEZE waiting for it to start!

That said...I have a pair of Asics Thermopolis running tights that I absolutely could not live without.  They seem to keep me comfortable no matter how cold it is, and if it turns out a little too warm for them they never get clammy.  They are probably the biggest reason I've gotten off the treadmill and on the road this fall.

As for a top, I found a mockneck compression top I that's worked really well just worn over a sports bra.  There is a TON of cool weather clothing out there to choose from, and I've found it to be worth the $$ to spend a little more and get the more technical gear rather than just a cotton blend that retains moisture.  

I found a really lightweight skullcap by Nike that is perfect, not too heavy but still cuts the cold and doesnt overheat you once you get moving.  I also have a set of the matching lightweight gloves by Nike and my hands stay plenty warm.  

i have fallen in love with nike dri fit cold weather gear. i've been wearing that for the past 2-3 weeks and it's been wonderous. i picked it up from marshalls and it was marked down significantly (pants 14.99, regular price around 40 i believe....shirt 24.99, regular price around 50). i told me girlfriend  all i want for christmas is more of that!! it was kept me warm and snug on my cold weather runs. i did a turkey trot two saturdays ago and the temps were in the 20s with the wind blowing. now mind you, i did have some other layers on, but if it weren't for the snuggness of the nike gear, the wind would have gone all through my body. for weather that is not so brutal, i have just been wearing that with shorts and t shirt over it.