On Tuesday, a day of record-breaking heat, I overheard a coffee shop conversation. "Sure doesn't feel like fall," someone blurted.
On the contrary, I thought. Nature is screaming that autumn is here. But then, nature responds more readily to light than to heat.
That's true of plants and it's true of birds. Plants ripen as sunlight wanes, and the landscape is not as green as it was, but instead turns a rich assortment of yellow, gold and brown. The landscape is filling up with birds, which migrate in response to light.
A Wednesday drive north along the valley's edge provided ample evidence. As I drove, I flushed flocks of meadowlarks from the roadside. Meadowlarks aren't thought of as flocking birds, but these groups of 10 or a dozen birds were larger than family groups would be.
American kestrels were frequent on fences and overhead wires, and red-tailed hawks on hay bales and posts.
These species are nesters here, but their numbers grow, and they become more conspicuous as the season advances.
At the same time, some birds disappear. The barn swallows are gone from our place west of Gilby, N.D., and I saw very few of these birds as I drove.
Likewise, the orioles are gone, and the sparrows have become inconspicuous.
But the blue jays, secretive and inconspicuous during the summer, are back at the bird feeders in the back yard.
Canada geese provide further evidence that fall is here. The geese have begun congregating in harvested fields, where they glean spilled grain and graze on emerging weeds. They're preparing for migration.
This is a relatively recent phenomenon this far south. Geese were practically eliminated as nesters early in the 20th century. A vigorous reintroduction program was undertaken, and geese have become a part of our summer bird life again - too big a part, some feel, since Canada geese can be a nuisance, especially in parks and on lawns and golf courses.
The geese are following their ancient habits, pairing up to nest in spring, then gathering in large flocks before migration. That's happening now. Bird scientists call it "staging."
Not all Canada geese will go south. The area below Garrison Dam on the Missouri River has become an important winter residence for Canada geese, and in recent years, some geese have spent winters near Grand Forks, on the city's sewage lagoons.
Geese are tough birds, able to stand the cold. What they need is open water and available food. Only extreme cold and heavy snow will send them away.
Canada geese are the common migrating geese in the Red River Valley. This, too, is a change. Not so long ago - a couple of decades - huge numbers of snow geese passed through the valley. Their numbers are much fewer now. Snow goose migration routes have shifted westward. Biologists suggest this is a response to changes in agriculture. Row crops, including corn, have replaced field crops, including wheat, on tens of thousands of acres in the valley. Geese have followed the crops westward.
I was on the road early Wednesday, and geese were on the move. The sunrise was extraordinary that day, no doubt due to dust from the harvest and smoke from western fires.
The air seemed heavy that morning, perhaps a result of the heat and humidity forced north by the weekend hurricane in the American Southeast.
The heat, we know, was record breaking.
Atmospheric conditions produced another phenomenon, a mirage, one of the most distinct and extensive that I've ever seen. The Pembina Escarpment was to the left of state Highway 32 as I drove north. Normally, the landscape would fall away to the east, into the vast flatness of the Red River Valley. Instead, the horizon was lifted up, and instead of an open plain, it seemed as if I were driving in an elongated bowl, a broad valley with hills on either side. Of course, that's what the Red River Valley actually is - but it takes special conditions to see it that way.