I like to keep my bike in the car on days I drive to work, in case I need it to get to a meeting in another building. However, I'm concerned that it gets too hot some days. Is there a temperature at which bike components might overheat or be damaged?
Possibly carbon bikes are a problem, but a regular steel/aluminum bike will have no trouble with "reasonable" heat (such as the inside of the average parked car) for a few hours. The biggest dangers are blown tires (if they were near their pressure limit to begin with) and melted plastic parts.
If left in a regularly hot place for weeks/months/years, however, eventually the grease in the bearings will break down and ooze out, plus the heat will take a toll on paint, tires, and plastic parts. And electronic parts are apt to be damaged.
I've heard of tyres exploding if inflated close to their limit when cold, then left in a hot confined space. But unless you're running your tyres at 100 PSI and up, I wouldn't be too worried. But perhaps someone with more knowledge will chime in; I'm just hazarding a guess about that. I don't think there's anything else on a bike you'd need to worry about though, not as far as temperature goes, anyway.
Carbon fibre doesn't like UV. Most if not all carbon fibre products use UV-protective resins in their construction to avoid delamination from prolonged exposure to sunlight. I'd be a bit suspicious of cheap n cheerful carbon parts.
To be on the safe side, let your tyres down a bit and keep a white sheet over the bike when it's in the car. Probably a good move anyway; a bike is a good reason for a car thief to break in... it doesn't matter if your car's alarmed; they're stealing the perfect getaway vehicle!