I tried to start my car yesterday after 1 1/2 weeks of no use, and it won't start. It doesn't sound like the engine is turning over - there is a soft rattling noise, not revving... all the accessory lights and head lights work, just not the stereo. Had the car checked in March and all was good. I am in Chicago, and we had a record breaking heat wave and humidity the last two weeks - could this have something to do with it, or any other ideas? Should I try to jump it?

I don't know that much about cars... but if you are getting kind a ticking or like you said "rattling" noise when trying to start it, the battery may be dead. You can try jumping it, but due the heat and depending on how old it is, it may not work and you may just need to purchase a new battery.

Perhaps someone has a better idea, but for now that's what I would say it is.

The engine doesn't start, the accessories work good, so the battery should be all right, and you hear a rattling noise when you go to start it? Could be the starter gear. Though if the battery is older then 2 years or so, well yeah the battery may not have enough juice, but if the accessories work, it most likely isn't.