POSSIBLY freeze, thaw, freeze, thaw, freeze, thaw.

Car could have been parked the entire winter, icicles building between roof and car, warmer weather starts thawing them, icicles slide down the window towards hood, new freeze comes, starts building new icicles, rinse and repeat.

I mean.. I'm not sure how it would cover the car so damned evenly, with such even-length icicles.. but I guess I could possibly maybe see it happening... weirder shit has happened.

Perchance.

Or, more likely, it's someones art project, and man-made.

Edit: had another look, You can see that the entire row of icicles have been snapped off along the roof, and you can tell the icicles have been stabbed into the snow over the car. I.e: art-project.
Car was covered in snow, someone snapped off icicles and made a motorized hedgehog.