During Louis's first trip to the burial ground, some lightning is seen near the horizon. Thunder follows about a second later. The lightning appears miles distant, and the thunder would have taken much longer to reach Louis's location.
When Ellie begins climbing the barrier in the "pet sematary", she accidentally kicks what appears to be a hornets nest, and is stung on the leg. Judd appears and immediately removes the stinger, and applies a dab of mud as first aid. Hornets do not leave their stingers behind when they sting. Only bees do this.
When the tanker truck swerved to avoid Gage the trailer becomes detached from the tractor which leads to the tragic death.
However, in real life this would not have happened, and the whole truck unit would have simply crashed into the ditch.