When the couple are running to the Super-K-Mart during the hailstorm. The hail is only on them. If you look closer to the shop, there is no hail falling onto the car park. When they run to it, the area that the hail falls moves with them.
It's not a K-Mart. It's a Walmart. I've only seen the movie a few times, but the most recent viewing was with my boyfriend, who teased me about the scene because I used to work at a Walmart.