To start with, Mondrian picks an unusual angle for his subject: the windmill is shown in close-up and is only partially visible. The painting avoids the obvious and over-familiar image of a windmill silhouetted against the horizon with all four sails visible, and instead emphasises that the windmill is a constructed edifice.
The viewer can see beams, rafters and other aspects of the building sticking out of the semi-abstract surroundings; most prominent of all is the doorway, seemingly beckoning the viewer to come in and explore.
Although Mondrian would later move towards pure abstraction, Windmill in Sunlight is an early work that shows clear impressionist influence. The windmill is surrounded by an ambiguous red-and-yellow body that could be read as either a field of wheat or a river.
Above it, the sky is represented by a fragmented mass of blue and yellow shapes that form a stark contrast with the red and black tones of the windmill itself. Here, Mondrian is clearly making an attempt to invoke the optical effects of bright sunlight: his painting captures the result of seeing light spreading across a clear blue sky.
The amount of reds used in the painting suggests that the scene is taking place at either sunrise or sunset, although this too is ambiguous.
Piet Mondrian's subsequent career unabashedly embraced all things modern. With this in mind, Windmill in Sunlight is a decidedly old-fashioned painting: it celebrates, in warmly nostalgic tones, a picturesque way of countryside life, worlds apart from the urban-influenced abstract imagery for which Mondrian ultimately became known.