I narrowed down to a single seed with ease. Since I have not experienced any meteor showers, I used a simple method of elimination by looking at some of my 600+ screenshots and determining if the weather on specif day at a specific time is
A. Unknown (rain/snow)
or
B. Unknown (no rain/snow)
Since according to Ninji, rain will last the whole hour, it makes selecting option A or B super easy with no margin of error*. I didn't even need to fill in very many days either. I recommend everyone who is finding this daunting to use the same method
After narrowing it down to 1 seed, I tried matching it against past screenshots, and it all seemed good except for one screenshot in particular. It was of a non rainy hour, but the weather seed tool claims it should have been raining at the time the screenshot was taken.
*I created a new character on this specific day, so I had to double check, and sure enough, creating a new character literally suspends the rain and messes up the weather for that day. So there's a TIL for you.
One disappointing thing most of all is the tool does not show which days you will get lightning. I've only experienced lightning once since March 20th. I would love to know when I can experience it again.