"may you" is a short list of wishes for someone the speaker cares about. Each one pairs a part of the person with a picture from everyday life: eyes that glimmer like fresh snow on a clear winter day, a smile as warm as a late summer sunset. These images are bright and gentle. The snow suggests sparkle and clarity, while the sunset brings in a softer, golden kind of comfort.
The last wish is the most surprising. The speaker wants the person's heart to smile "as if it were your dog when you come home." After two grand images from nature, the poem lands on something small and familiar, and that shift is what makes it work. A dog greeting its owner shows joy with no hesitation or holding back. The speaker seems to hope this person can feel happiness that openly and easily. The mood is tender, warm and a little playful, like a kind note from a friend.