This morning my car started briefly, then stopped. Thinking little of it, I went to start the car again but instead of turning over and starting the engine just made a whirring sound as if the starter is spinning but not engaging.

Wtf?

It was considerabely colder this morning than usual here in Los Angeles so that may have something to do with whatever part decided to spontaneously malfunction. Additionally I know they battery connection isn't the greatest as it has considerable corrosion on it and just a few days ago my car wouldn't start at all because it wasn't getting enough current to turn over until I cleaned the terminals.

It is possible that a lack of current is causing the problem or is it more likely that some component under the hood (starter, solenoid?) decided to quit on me. How much could the change in temperature be affecting things (roughly -20 degree change since last time it ran 3 days ago)? Any insight would be greatly appreciated.
...turns out the battery was just low, presumabely because of the weather. I have no idea why the starter was making that funny noise and not engaging, but when I hooked up a pair of jumper cables it cranked and eventually started.