A couple of days ago we had what the forecasts call a “wintry mix,” which always sounds to me like something you’d set out in bowls at a ...tail party this time of year. It was, in fact, rain, snow and sleet mixed with salt and the sludge that gets thrown from the treads of tires. One minute, snow was falling, and the next it was raining. The sky was the color of duct tape, and it let about that much light through. What a “wintry mix” does is make you want to stay home — or obsessive about your travels, anxious simply for the pleasure of getting home again.

It’s the difference that makes a day like that so interesting. Till now, this has been a bright oaken autumn. The most vivid colors came and went, leaving behind the oaks, which hold their leaves far longer. The last few weeks have been dusted with a dry, clear light, and the oaks have shown just how various and brilliant their colors can be. It was as if the oaks had all stepped forward to remind us of a spectrum of color that goes unimagined the rest of the year.

But everything changes on a wintry day.