Cattle in the Heatwave shows a group of cattle gathered in the shade of a large tree on rising ground, with open country falling away to a low horizon beyond. The tree stands left of centre, its full summer canopy worked in soft greens and greys, and the cattle are grouped beneath and just clear of it, three or four animals in brown, grey and white, standing close together at the edge of the shade. The land around them is dry, painted in pale gold, ochre and muted green, with a track running down to the lower right. Behind, the ground opens into hazy fields and hedgerows that thin towards the distance. The sky fills the upper half in warm cream, pale gold and soft pink, hazed over so the light reads as heavy and diffused, with the sun's warmth spread evenly across the whole scene rather than falling from one clear point.

The paint is handled softly for the most part, with the sky and distance blended and hazed, and the tree's canopy broken into looser, drier touches at its edges. The cattle are set down in a few loaded strokes, their forms kept simple against the shadow beneath the tree, and the foreground grass carries thicker, drier marks of gold and green that suggest parched summer growth. The muted, high-toned colour throughout holds the sense of heat and haze across the picture.