I got the low fluid warning as well...had it over the last few days, although it was not caused by a cold snap, it was 60 degrees...I used the windshield wiper fluid MAYBE 3 times, so i know i did not run out, but i am hoping maybe the dealer did not fill it up all the way and only had a little left when i used it all up...
I dropped off the car at the dealership today due to the wind noise that some F30s are experiencing and I mentioned the low fluid warning as well, so we will see what the issue ends up being for that....