Helen spends every winter in the North during her childhood, and that is where she experiences snow.
Helen is very excited during her first big snowstorm, even though it is somewhat scary. She describes a visit to a New England village in her childhood when she was able to “enter into the treasures of the snow” (Ch. 12). This was something that delighted her, though she could not see or hear it. She could still experience it with the ways of communicating she had developed.
On the third day after the beginning of the storm the snow ceased. The sun broke through the clouds and shone upon a vast, undulating white plain. High mounds, pyramids heaped in fantastic shapes, and impenetrable drifts lay scattered in every direction. (Ch. 12)
This incident shows that Helen Keller could still live a very full life, and enjoy new experiences, even though she did not have all of her senses. See how vividly the visual descriptions are included? They must have been described to her using her signs. Then she wrote them for us.
Even if you cannot see and hear, there are plenty of senses left in a snowstorm. You can still feel the cool wind on your face (she says, "air stung my cheeks like fire"), and taste the icy snow, smell the pines in the air, and feel the crunch under your feet. I imagine that between the descriptions and these other senses, she was able to imagine the rest.
Our favourite amusement during that winter was tobogganing. In places the shore of the lake rises abruptly from the water's edge. Down these steep slopes we used to coast. We would get on our toboggan, a boy would give us a shove, and off we went! (Ch. 12)
A snowstorm is like sensory overload. I think this is probably why little Helen liked it so much. Even though she did not have use of two of the main senses that we have come to rely on to experience the world, she could use the others much more during this time. Most little kids love playing in the winter snow, but when you live in the dark, everything takes on that much more meaning.