I'm sure you wouldn't think twice about catching a snowflake on your tongue, but using snow to make snow ice cream or melting it for drinking water might get you wondering whether it's safe or not.
The Bottom Line
Yes, you can eat snow! Snow is crystallized water, meaning it's actually more pure than most types of precipitation. If you think about how snow forms in the atmosphere, it's essentially frozen distilled water, crystallized around a tiny particle, so it might even be more pure than the stuff coming out of your faucet. Campers and mountaineers all over the world use snow as their primary water source without incident. Even if you live in a city, you can eat clean snow.
Snow does fall through the atmosphere before hitting the ground, so it can pick up dust particles and other impurities in the air. If the snow has been falling a while, most of these particles have already washed out. The biggest consideration for snow safety is where and how you collect the snow.
Safe Snow Collection
You don't want snow that is touching the soil or street, so either scoop up clean snow above this layer or use a clean pan or bowl to collect fresh falling snow. If you intend to melt the snow for drinking water, you can ensure extra purity by running it through a coffee filter. If you have electricity, you can boil the snow melt. Be sure to use the freshest snow you can find, since the wind deposits a fine layer of dirt and pollutants onto the top layer of snow within a day or so.
When You Shouldn't Eat Snow
You probably already know to avoid yellow snow. The color is a big warning sign the snow is contaminated, in this case with urine. Similarly, don't eat other colored snow. Red or green colors can indicate the presence of algae, which may or may not be good for you. Why take the chance?
Other colors to avoid include black, brown, gray and any snow containing obvious particles of grit or grime. Snow that falls around smoke stacks, active volcanoes, and radiation accidents (think Chernobyl and Fukushima) should not be ingested.
The most common warnings about eating snow concern eating snow near roads. Exhaust fumes used to contain lead residues, which would get into the snow. Toxic lead isn't a modern-day concern, but it's still best to collect snow away from busy streets.