They said fire just happens with the intense sunlight. I was doubting this, maybe I'm still doubting it.
Of course, many fire incidents are caused by humans, though wildfires do happen naturally Kingsley and are one of the major effects of climate change too. One just needs three things to ignite a fire and those are oxygen, heat and fuel. So Intense heat from the sun or just a lightning strike can result in a fire if there is enough dry biomass to fuel that fire or spark.