After thunderstorm / rain, it carries on visually raining but it is not really raining. The sky will still look the same as in rain / thunderstorm, the rain that is not really there will still render. 

How to reproduce: 

1. do /weather rain
2. Sleep in a bed or do /weather clear
3. Rain is still there 
4. Verify this by attempting to throw a riptide trident. It should not work. 

Reloading the world will correct the weather.