Constable on clouds

The standard publication about weather available during Constable's lifetime was Thomas Forster's Researches about Atmospheric Phenomena, published in 1812, which Constable thought "was far from right." Constable identified the clouds in one of his studies as "cirrus." He was therefore familiar with the terminology created by Luke Howard, who published in 1818 a classification of cloud formations. From Walker's book on Constable:

Constable considered his own empirical studies as reliable as the work of these early meteorologists, and in the same 1836 letter to George Constable he wrote: "My observations on clouds and skies are on scraps and bits of paper, and I have never yet put them together so as to form a lecture, which I shall do, and probably deliver at Hampstead next summer."

By "next summer," Constable was dead. 

This night watercolor was painted facing northeast in light rain with scattered clouds and light wind. Ambient light reflects back into the lower clouds and makes the scene brighter. It was, however, painted about 9:30 at night.