Memory vs. Novelty
As summer unfolds, so do memories of summers past, many from childhood. These snippets seem to suggest, "This summer will be like those were." But no summer can be like those were. Powerful expectations, based on real memories as provoked by deeply familiar seasonal changes, are just as powerfully turned back. Not sure if "poignant" is the right word for this; there's something concrete and finite about it, though.