if its raining heavily then it might be bit dark and due to this, headlights (and rear lights) should have turned on by itself. Isn't it?
i have noticed tht even if its drizzling and cloudy which makes the outdoor light darker then M3 automatically turns on the headlights.
they gave me the first date option as 'Saturday' only but i had some pre-booked plans, therefore, I booked for the next date which is Monday. So, delivery on a Saturday is really not a favour from tesla.