How many evenings are there? There are many.
To remember the reading た we use the word "Taco"
Let's start with the kanji meaning: many. You go outside in the evening (because that's what this kanji is made up of) and are surprised when you're hit by many tacos flying from the sky. For some reason it's raining tacos, and of course you have no idea why.
Currently there are no similar looking kanji which exist in the WaniKani learning system