 I don't know if I've ever experienced this. Want to come to my house for a barbecue after the show? The process can be accelerated by higher temperatures if the watermelon isn't kept cool after being harvested. Heat can also cause fermentation, leading to watermelons potentially exploding. I was at a watermelon festival once, and I heard that, and I just took off, let me tell you. If a watermelon explodes, some guy takes a knife and cuts into it.