2005 matrix runs rough and stalls in warm weather

Have you had any work done on it before this started? A disconnected mass airflow sensor can cause those symptoms. If it is plugged in, it could still be bad. I would have the car scanned and codes read first before replacing it though as they can be a bit pricey. Also ensure your intake piping is all connected to the engine (to the intake manifold/throttle body specifically). if the air intake isnt making it to the engine and thus the mass airflow sensor wont be reading the air temperature and all that so the car will not run for longer than a minute if that.