Brake Warning Light Coming On, Why would this happen?
 

Over the last couple of months I've had the brake light coming on. It comes
on only when I brake and only happens when the car is cold. After driving
about 10 to 15 minutes the light stops coming on. I've also noticed it tends
to happen only when it's colder out, when the temperature is in the 50s or
so.
I've checked the fluid level and it's fine. The element that checks the
fuild level seems to be moving freely. I haven't changed the fluid in a long
time, although I don't think that's the source of the problem because the
fluid is still fairly clean. I've considered the parking brake switch, but I
find it odd that the light coming on coincides with me braking the car.

One thing I want to make clear is that this is the brake light, the same one
for the parking brake, not the ABS light.

Any ideas would be much appreciated.