Three short lines, and the whole poem hangs on one surprising move: a memory turns into a taste. The speaker thinks back to childhood, and instead of simply seeing or recalling those days, they feel summer arrive in the mouth, "bursting on my tongue." It sounds a bit like biting into ripe fruit, the kind of sudden sweetness that floods you all at once.
That choice of sense matters. Taste is immediate and physical, so the past doesn't feel distant or faded here. It feels present and alive. The word "sweetness" works two ways, suggesting both actual flavor and the happy, uncomplicated feeling of being a kid in warm weather. The speaker seems delighted rather than sad, with none of the aching distance nostalgia often carries.
The mood is bright, warm, and a little playful. The title, "Sunspek," hints at a tiny speck of sun, which fits a poem that packs so much light and flavor into so few words.