Cloud study 1822, oil on paper, 7.8 x 12.6 inches
I found these wonderful oil sketches by John Constable while searching for great plein air paintings. This summer, I'm going to be painting landscapes outside, which I've never tried (although I've sketched outdoors before). I'm really looking forward to it.
Cloud study with birds in flight, and Stratocumulus clouds 1821
oil on paper on board, 9.8 x 11.9 inches
You can see more examples of Constable's cloud studies on the National Gallery of Australia website.
Study of clouds 28 July 1822, oil on paper, 11.5 x 19 inches