I had a few meteor showers and heavy rain, but no thunderstorms. Every time it was announced by Isabelle beforehand. There will also be nights where there were 'mini' meteor showers, like 6-7 consecutive shooting stars. The times I had a metor shower were of course when my joycons were drifting, so I didn't get half as many star fragments as I could have
i've had the game since launch and literally had 1 rainy day. no thunderstorms. i have however, had a few meteor showers with 20+ frags, so maybe all my rng luck went to meteor showers? lol
From my experiance meteor showers are when shooting stars happen constantly all night. Sometimes Isabelle announces it but some people say it happens even when she dosent. I personally have not had one yet. I don’t TT and I’ve had the game since day 1. But what I find works is waiting for a clear night (it being clear is important), if I’m not busy, I leave my character in a good sky-viewing spot. Then put my switch volume all the way up. U will hear shooting stars happen. I usually get 5-10 stars randomly within an hour. I think u can get only 20 stars max a day?
Anyway hope this helps