When a vehicle has been in the heat, not running, and the sun's daytime warming has heated the interior, initial running the A/C system on RECIRC will help provide better cooling than with RECIRC turned OFF.
When a vehicle is under the outside condition that was just described, the cabin air temperature can reach upwards of 140 degrees. Now it's just not the air at that temperature. All surfaces (dash pad, steering wheel, door panels, etc.) are also at or near the same temperature. The A/C systems needs to lower both cabin air and surface temperatures. Assuming it's still hot outside, you don't force additional hot air (from the outside) across the evaporator. You want to chill the air in the cabin first.
When the cabin temperature is cooler, then take the system of RECIRC. To help remove the temperature when first starting the vehicle, open and keep a door or two open, or lower the windows to let the heat out.
In RECIRC mode you're not completely shutting off outside air from coming in. Around 5% fresh air comes in. This is like this across most vehicle manufacturers.
Also make certain the cabin filter is clean.
In DEFROST mode, RECIRC will be disabled. This is to prevent the humidity from our breath, moisture from wet clothing, etc., from causing windows to fog over. The fresh air coming in, along with A/C compressor running, will reduce the humidity in the car. Sometimes in winter even when the climate control is not in DEFROST, windows can fog over. Turn the A/C ON to reduce the humidity in the cabin.
If you want to see how hot it gets in a car, or how the A/C system is performing, insert a small cooking thermometer into the center dash vent and keep it there. You'll may be surprised at what temperatures you'll see on the thermometer.
