Although most of the movie takes place during a weekend, the weather is constantly changing back and forth from cloudy and rainy to sunny and dry among scenes that are close in time from one another. It's impossible for the weather to change that quickly in one direction let alone to do it back and forth over the course of a few hours.
At 1:29 of the movie Walt is driving down a residential street on his way to retrieve his tools, you can see the truck going in the opposite direction swerve into Walt's lane to avoid the film crew in the street. The two-tone gray Toyota truck (at 1:29:20) has Washington State license plates. This movie was set in Washington State, but was filmed in the Metro Vancouver, Canada, area; more specifically, Walt is living at 20657 (at 0:12:55) Dolman Street (at 0:02:15) which is in Maple Ridge, British Columbia, in the Metro Vancouver area, so the probability is high that the truck was part of the film shoot. If an error were committed then it was that they didn't use a telephoto lens or Steadicam so the camera could have been out of the way.