I created a superflat world to test some things out within the newest versions of Minecraft, when I noticed that it started to rain really early after creating the world. It also was a thunderstorm as well. After clearing the weather, I continued what I was doing in the world, when about 5 minutes passed and it started to storm again. I kept clearing the weather, and it seemed that every 5 minutes or so it kept thunderstorming.
 
What I expected to happen was...:
After I cleared the weather, it should not storm so frequently (or at least not be a thunderstorm every 5 minutes).
 
What actually happened was...:
Instead, about every 5 minutes or so, it started to rain and always kept turning the weather into a thunderstorm.
 
Steps to Reproduce:
1. Create a default Superflat world.
2. Wait approximately 5 minutes for it to start raining.
3. Notice that when it starts raining, it turns into a thunderstorm. Also notice that after clearing the weather, in another 5 minutes or so, it will thunderstorm again. And it keeps repeating as long as you keep clearing the weather or let it finish by itself.