If the air temperature is -14 degrees F or colder, this is a fun experiment to do ( as long as it's below freezing it works, the colder the better)
Throw a large cup of boiling water into the air (not the cup, just the water) and it will turn to snow.
What I found works well is: fill a coffee cup (a microwavable cup) 1/2 to 3/4 full of water, put it in the microwave and bring the water to a rolling boil. Carefully but quickly go outside, throw the cup of water high into the air, (the water, not the cup) and watch it change from water to snow.
When extremely cold air moves in, it is usually very dry. Boiling water, on the other hand, emits a large amount of vapor - and that's why it steams. When it interacts with cold temperatures, the excess vapor crystallizes creating instant snowflakes. The colder and drier the air, the faster the water freezes.
Here are some tips to maximize the success of your homemade snowfall: