I don’t think that guidebook is accurate because everyone’s game has a different “weather seed” that determines the weather patterns for the next few years (including meteor shower days).
Another thing to keep in mind is that you may have a heavy meteor shower and not know it because Isabelle won't announce it if there's other news for her to announce that day (for example, a villager birthday or the start of a new season like wedding season or something).
There are 2 types of meteor showers, heavy and light. Heavy ones are announced by Isabelle in the morning if she doesn't have any other news to announce and villagers will talk about them throughout the day too. Light ones are just a few shooting stars and aren't mentioned by either Isabelle or villagers.
Celeste will only visit you if there's a meteor shower that night (either heavy OR light).
If you have enough weather data, you can find your island's weather seed to figure out when you'll have heavy or light meteor showers: https://wuffs.org/acnh/weather/
And if you use a weather forecasting tool (like the one on NookPlaza) and come up with Fine00, that means you will have a heavy meteor shower that night and most likely Celeste as well. Fine02, Fine04, and Fine06 means that you will have a light meteor shower (just a couple of falling stars throughout the night, maybe under 100, spaced out) and may give you Celeste and
I have't gotten a meteor shower either, maybe I have, but isabelle hasn't said anything about it and I don't talk to my villagers enough for them to me there is a meteor shower
Sooo I just used meteonook... found out that even if I played every day from day 1, my first shower would be September 17. Basically almost 6 months without one... And the next one isn't until the following April. Meanwhile, there are people with 3+ per month. Great. Makes complete sense...
Glad I time travel, because I am not waiting around for 10 years to get a meteor shower each zodiac sign...
I got lucky with MeteoNook - on the 16th I had a rainbow and yesterday I had shooting stars.
These two weather conditions - as well as a few more other inputs from me - gave me my weather seed within 4 days!
I have 13 showers in 2020 so I'd say they're rare... I also had Northern lights in Jan and Feb 2020 (before the game was released), and the next northern lights won't happen until Jan and Feb 2021.
I don't time travel so I won't experience them anytime soon