Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

Ah but my car's a convertible. I guess it'd be like unzipping the under arm vents for me.

Engines produce (on average) 3 times as much heat as power.

So, if yours is not the hairdressers version, you would be sitting in a vehicle with a 900bhp/660kW heater.

Losing the roof would certainly help, but I suspect that much heat would still make something of an impact.