I sit with open window

August 20. 

Rain all night and to-day, making it a little chilly. Though I sit with open window, I should think it uncomfortably cool with it closed. Some must have a little fire.

H. D. Thoreau, Journal, August 20, 1856

See August 20, 1858 ("It is still cool weather with a northwest wind. This weather is a preface to autumn"); August 27, 1860 ("The nights have been cooler of late, but the heat of the sun by day has been more local and palpable."); August 29, 1854 ("It is so cool that we are inclined to stand round the kitchen fire a little while these mornings, though we sit and sleep with open windows still.“); August 29, 1859(" It is so cool a morning that for the first time I move into the entry to sit in the sun."); August 29, 1854 ("I enjoy the warmth of the sun now that the air is cool.") Compare November 8, 1855 ("I can sit with my window open and no fire.”); October 31, 1854 ("Sat with open window for a week.”); February 18, 1857 ("I sit all this day and evening without a fire, and some even have windows open.”)