I'm not an unschooler, but I saw this in the new posts. I have been a huge weather geek pretty much my whole life.
A couple of things that I thought were fun when I was younger (probably more like elementary school aged, so you can just see if any of these sound like things your two year old would like)
The whole tornado in a bottle
Make a fun rain gauge
Make felt clouds, sun, lightning, snow, etc, and find a place to hang them. Every day hang either what it is like outside right then, or what the forecast says.
Make a rainbow outside with the water hose
Create fog by freezing a bowl, then pull it out and put ice cubes in it. Then pour warm water slowly on top. (make sure it's a bowl that won't crack from the temperature differences)
Demonstrate evaporation by leaving a large glass of water somewhere sunny (but not where rain will replenish it). Every day mark where the top of the water is.