Well, like I've already mentioned, all the Color Tamagotchis are supposed to reflect real weather patterns in Japan, depending on what time of the year it is. It's a feature that's pre-programmed into the Tamagotchi, I think, and not as a result of downloads to get that feature or the Tamagotchi somehow sensing what the weather is like in Japan or anything like that.
I haven't seen hail or sleet. There are only 6 weather patterns that you'll be able to see (at least on the +C; I haven't yet had in-depth looks for the iD/iD L, both of which I've only had since March/April of this year): clear, cloudy, rainy, typhoon/stormy, snowy, and occasionally, there's lightning by itself with the gray sky. When the winter time comes, it's just a rhythmic snow coming down. There is wind on the +C but it doesn't stand alone; it comes accompanied with the typhoon.

You'll know it when you see it. The wind rips up any trees you plant, there's lightning, a ton of rain, and the house sways (if you're outside in the garden, you'll be able to see it).
It's like the above picture. Typhoon season has already started, so I wasn't really surprised to see this yesterday.