A hot summer night keeps the speaker awake, and the poem follows what they notice while lying there. The moonlight looks cool, but the speaker calls it an "illusion of coolness," so the relief is only a trick of the eye. Then a warm breeze arrives, and fireflies blink out of the dark. The katydids add their own sound, which the poem hears as a chant of "full moon full moon full moon." A passing jet cuts into this natural scene, a small reminder of the human world beyond the yard.
The ending is the strangest and funniest moment. Staring at the moon, the speaker wishes to be "buried up to my neck." That image suggests a longing to be cooled by the earth, held in place, and made part of the night rather than tossed around in it. The mood is drowsy, restless, and quietly playful. The speaker is uncomfortable but also deeply attentive, soaking in every light and sound.