It's going to be 30-40 degrees F tomorrow morning at 8am in NY and i'm wondering if you guys wear anything special on your heads for this kind of weather. I'm going to commute 5 miles to school on a roadie so some suggestions for headgear might be nice.

I've done 50 degrees without anything on my head but a helmet so would 40 degrees make a big diff?

For 5 miles, you could probably get away with not much. Here's my dress according to temps (remember, where I live it's 80% or more humidity year-round).

50+ degrees: shorts and a long sleeve shirt
40-50 degrees: shorts and several layers, at least 2 long sleeve shirts, and a wool hat under my helmet
30-40 degreesrevious layers, plus a jacket, and wool socks, maybe leg warmers too. Ski gloves.
20-30 degrees: long pants over leg warmers, wool socks, 3-4 layers under my jacket, 2 hats, and something covering my face. Ski gloves.
10-20 degrees: it doesn't get that cold here.

yes hat and definitely gloves, doesn't need to be super heavy ones.

I know that for me I don't like riding in the 40's at all without something to at least protect my ears from the wind. The 30's I wear a beanie\skullcap, but when it's a bit warmer in the mid 40's I'll wear a headband since the hat is too warm. Above the 50's is when I don't wear anything on my head.

I don't wear anything on my head until temps get below freezing otherwise I overheat. I am cold when I start out, but I climb a couple of hills at about the five minute mark and am nice and warm after that. I ride 18 miles each way, takes about an hour.

When I do put something on, I like those Novara fleece skull caps you can get at REI. Very thin but warm and reasonably priced.

I wear a lightweight Turtle Fur fleece skull cap. You need to pay attention ot the cut when you get a skull cap. I prefer something that is cut lower in the back so that my ears are covered. Generally its the ears that get cold before the rest of your head, so you need to make sure they are covered.

Paul

I too did my first bike commute in a couple of months in NYC today.

Paid for it. Bike needed a cleaning and a half after. Still melting snow, lots of dirt, and piles of Salt. My Cyclo was a mess.

I commute year round. Besides the normal clothing I wear for the winter I also keep a spare hat and thin gloves in my backpack. For 30's or 40's i prefer having my head covered even though it's usually my ears that get cold.

I generally only start thinking about wearing something on my head (other than my helmet) below 35 or so. I've ridden down to about -25, at which point I'm wearing a gaiter, a balaclava and a neoprene face mask. In between, I just put on what seems like a good idea at the time.

Even if I start out quite cold, within about 5 minutes I'm making enough heat that it's not a big deal. My ears need to be covered. I was riding a few days ago at 15*F with a stretch gaiter up over my head and ears but with my face completely uncovered. It was fine after 5 or 10 minutes, a little too cold before that.

Nothing special.

Wear a hat. If it's too warm, take it off. Or take a hat and if it's too cold, put it on.