Nikon D90 DSLR, how low a temperature can it withstand?

I live in Chicago and a friend and I will be going on a shooting spree (a photo shooting spree). The temperature here will be between the 19 and 23 degrees. Is that too low to have my camera exposed to the cold? We will be outside most of the time and I will most likely have my camera in the bag sometimes, but most of the time will be out. What do you all think?

We will be shooting around downtown and the lakefront.

Added (1). Ah ok, thanks for the suggestions. I do have 2 batteries.so, I'll be taking them. I just gotta make sure they're charged.

Now, what do you think of these pictures.

University of Chicago

Chicago from Roosevelt Rd bridge overlooking Metra trains

Starved Rock French Canyon in Illinois fall 2010.

I'm an amateur photographer. I would appreciate your constructive criticism.

Take extra batteries if you have them, other than that, you will be fine. Very cold temperatures shorten battery life.

The battery will not take as many shots once it gets cold.

Those of us who shoot in cold weather routinely, keep a spare battery in a pocket close to our skin to keep it warm. As the power in the cameras battery starts to wain, we switch batteries and start the process of warming the cold one.