HA! I thought it was going to be more like a "Weather Rock":
1. Take the umbrella outside with you.
2. Open the umbrella.
3. Check its topside surfaces.
- If it's wet, it is raining.
- If it's icy, it is raining and the temperature is very cold.
- If it's dirty, it is windy and there is dust around.
- If it's white, it is snowing.
- If it's hard to see, it is night time.
- If it's gone, it is very windy!
- ...