Which of the following is NOT a cause of wildfires?

Rainfall is not a cause of wildfires because it typically serves as a mitigating factor in fire spread. When an area receives sufficient rainfall, it can increase moisture levels in vegetation and soil, reducing the likelihood of a fire igniting and spreading. In contrast, lightning, campsite fires, and controlled burns can all initiate wildfires under the right conditions. Lightning strikes can ignite dry vegetation, campsite fires may escape control if not properly monitored, and controlled burns, while intentionally ignited for land management purposes, can unintentionally spread into wildfires if conditions are not carefully managed. Thus, rainfall is the option that does not contribute to the occurrence of wildfires.