I drive a Honda Insight 60 miles to and from work every day.

Once the temperature is below 41 degrees, the AutoStop feature is disabled. This means the engine does not stop running at red lights and therefore the heater will continue to pride heat. The reason is that the catalytic converter would cool down too much and not be within its operating range.

Above 41*, you do have the option of letting the engine go into AutoStop, but leave the interior fan running. This will provide heat using the coolant in the heater core, but after a few minutes the heat starts to subside. In theory, by then, the light should have turned green and the engine would be running again.

During summertime, when using the AC, you have the option of letting the engine turn off at red lights or continue running. In the Insight, with the engine not running, you do not have AC. I believe the Prius's AC still works when the engine is off, as it's compressor is more like that of your refrigerator.

In either situation, if either the heat or the cold is too much to bear, lifting your foot off the brake will restart the engine and provide heat or AC.