The Dewy Morn by Richard Jefferies

In August the loveliest day is when the thunder booms far off at sea, while over the cornfields the sun shines with increased brilliance. The sky over the wheat is blue, but in the distance some large clouds stay motionless. The upper slopes of these mount-like vapours reflect the rays of the sun, beneath they melt away in an indefinite mist which does not throw back the light. The massy ridges above have no foundation beneath reaching to the horizon; they do not threaten; they add to the beauty of the level azure, as hills about a plain.

Rolling in from the south comes, the wave of heavy sound, too distant to cause uneasiness -- the boom of an immense breaker on the shore of heaven. After each burst the sun seems to glow fiercer, the warm haze thickens, the rich blue sky is richer, the insects in the air vibrate their wings more rapidly, and a shriller hum arises; butterflies are busier, and in the wheat the reapers bend, cutting at the yellow straw.