Immediately.

Watts, November Evening in a Welsh Wood, 1893

This month taxes a walker’s resources more than any other. For my part, I should sooner think of going into quarters in November than in winter. If you do feel any fire at this season out of doors, you may depend upon it, it is your own.  It is but a short time these afternoons before the night cometh in which no man can walk. If you delay to start till three o-clock, there will be hardly time left for a long and rich adventure, to get fairly out of town. November Eat-heart, is that the name of it? Not only the fingers cease to do their office, but there is often a benumbing of the faculties generally. You can hardly screw up your courage to take a walk when all is thus tightly locked or frozen up, and so little is to be seen in field or wood. I am inclined to take to the swamps or woods as the warmest place, and the former are still the openest. Nature has herself become like the few fruits she still affords, a very thick-shelled nut with a shrunken meat within. If I find anything to excite a warming thought abroad, it is an agreeable disappointment, for I am obliged to go willfully and against my inclination at first, the prospect looks so barren, so many springs are frozen up, not a flower, perchance, and few birds left, not a companion abroad in all these fields for me. I seem to anticipate a fruitless walk. I think to myself hesitatingly, shall I go there, or there, or there? And cannot make up my mind to any route, all seem so unpromising, mere surface-walking and fronting the cold wind, so that I have to force myself to it often, and at random.

But then I am often unexpectedly compensated, and the thinnest yellow light of November is more warming and exhilarating than any wine they tell of. The mite which November contributes becomes equal in value to the bounty of July. I may meet with something that interests me, and immediately it is as warm as in July, as if it were the south instead of the northwest wind that blew. 

Henry David Thoreau, from his journal, 25 November 1857