Rain particles all collect before disappearing while in the inventory

After searching in the inventory when it is raining for a little bit, when you go to exit out you will see all the rain particles on the ground then disappear. This may be a tiny bug but it is a big one to people that don't have very good phones, computers, or tablets, and may cause many people to lag. If you could fix this that would be very appreciated, thank you.

Repo steps:

1. Have Pocket UI as the active UI format,
2. Give yourself an effect that lasts at least long enough that this will be testable for (can do the maximum 1000000) and it can be any potency,
3. Open up any Pocket UI interface that takes up the whole screen (Chest, Furnace, your own inventory, etc.),
4. Wait at least 10-20 seconds
5. Close the Pocket UI

Edit by PHO:
According to MCPE-16483, the bug affects not only raindrops but all kinds of particles are accumulated, including runes from an enchantment table and smoke from a nether portal.