Snow is one of the richest sources of natural nitrogen. Rain contains nitrogen as well, but usually runs off before any measureable amount has a chance to soak in.
When I was a kid growing up on a farm we would (rarely) get a three day gentle steady rain. This was dubbed by all the locals as “a million dollar rain” not only for the slow sinking in of moisture but for all the nutrients it contained. Slow and steady wins the race, while fast and pounding only fills the ditches. Or something like that.
As I said, these rains were rare. Snow, on the other hand, was not. Because it soaks into the soil slower than rain, more nitrogen is absorbed from snow. The time it spends on the soil’s surface allow key chemical reactions to take place, while protecting soil’s micronutrients and bacteria.
While waking up to a frosting of snow out of season can cause much groaning and moaning, there is a silver lining in those snow laden clouds. Late spring or early fall are the best times for snow to deliver its cargo of nitrogen to the soil since it can easily soak in. The snow that falls during winter tends to sit on the surface of frozen ground and all too often is lost in the quick runoff come spring.
If given a chance to soak in, snow can deliver five to ten pounds of nitrogen per acre.
Late spring or early fall snowfalls are often called “poor man’s fertilizer” for the free dump of nitrogen they deliver.