This connects with the Scarlett Letter too. On a snowy day in Speak, Hairwoman asks the class what snow symbolizes in Hawthorne's book. Melinda thinks, "Hawthorne wanted snow to symbolize cold, that's what I think" (62.6). She seems to be talking about emotional cold. Melinda also equates cold with "silence" (62.6). She thinks, "Nothing quieter than snow" (62.6).
All this fits with the way Speak matches the turning of the seasons with Melinda's movement toward recovery. As the weather thaws, so does her heart. In the final chapter, we are told:
The tears dissolve the last block of ice in my throat. I feel the frozen stillness melt down through the inside of me, dripping shards of ice that vanish in a puddle of sunlight on the stained floor. Words float up (89.15).
Ice and cold of winter, heat and warmth of summer – these create an extended metaphor (a metaphor that plays out across the novel) that symbolizes Melinda's movement from frozen muteness to fluid speech.