At the beginning of the episode, Crater Lake is frozen over and Sean falls through the ice. Toward the end of the episode, when Sean and Clark are fighting on Lex Luthor's property, the pond is not frozen over. If the season is cold enough to freeze a lake, it should also freeze the pond.
Sean freezes the flames in the campfire/candles. This of course is impossible.
When Whitney is about to run down Sean, the rear window of Whitney's vehicle appears to be smashed before they leave the road and crash the car. However, the window is not smashed - it has water droplets on it giving it a shimmer, just like the driver's door window.
When Whitney nearly runs down Sean in his vehicle, the sound of Whitney slamming his foot on the brakes and screeching tires can be heard before Whitney actually slams his foot on the brakes, and before the car even begins braking.