The jam jar sitting on John Vannatta's kitchen table appears to be filled with coffee, until he shows you the label on the lid. The preserve inside is history, saved from a time when black blizzards filled the sky, turning day into night; a time when Americans starved. "Pure 1930s Blow Dirt," it reads. It might also say: don't forget, lest it happens again.
Not that Mr Vannatta, 92 – or his neighbour Huston Hanes – needs reminding. Both retired farmers, they are members of a very small club indeed: the last survivors of that great American epic, the Dust Bowl, that spanned 1932 to 1936 and coincided with the Great Depression.
Mr Vannatta found the dust on rafters in an old barn 10 years ago and knew at once what it was. When the storms they called "dusters" roared through, vacuuming whole fields to the heavens, this is the dust they left behind, choking the lungs of grown men and burying trees to their highest limbs.
Brought together by a reporter, the two neighbours in Keyes, a small and parched farming town in the Oklahoma Panhandle, ponder not just the past, but also the present. Drought is again stalking the Panhandle, a two-by-four stick of territory on the map so flat and so lonely that it goes by the name "No Man's Land". It has been more like a furnace here of late than either can remember, more even than when the dusters came. And they both agree the Dust Bowl, or something close to it, could happen again.
"We would have hot days, of course," says Mr Hanes, his hands wider than a baseball glove, as he recalls the Dust Bowl, an environmental catastrophe that would be blamed not just on the perniciousness of nature but also on the greed of men. It followed the wheat rush of the late 1920s when farmers ripped up millions of acres of buffalo grass and left loose topsoil exposed. "Those days were hot, but..."
They nod at one another. The recent string of afternoons when the thermometer has broken through 100 degrees Fahrenheit (nearly 38C) here is something new.
They also know they are not alone. This week we learnt that July 2012 was the hottest month the US has had since records began in 1895. The average temperature across the 48 contiguous states was 77.6 degrees Fahrenheit, 3.3 degrees above the 20th-century average.
But it's the loss of moisture that is causing the greatest concern. Half of all the counties in the US have been declared disaster zones, and drought of varying intensity now grips two-thirds of the nation, drying out rivers, scorching crops and forcing cattle farmers to sell herds they can no longer feed.
It will take more than the current drought – some relief is forecast for parts of the upper Midwest this weekend – to impress these men. "I didn't think it was ever going to rain again," Mr Vannatta recalls of the early Thirties. "It was so dry back then, I never did see a single rain in years that was anything more than a sprinkle." About the only precipitation he and Mr Hanes did see was the soil dropped by the dusters.
One of the first rolled through on a summer's day in 1932 just as Mr Vannatta, his mother and his uncle had crossed the Kansas line on their way to see relatives in Ohio. "It was so dark you couldn't see the front of the hood of the car, it was just black," he remembers. "We just kind of backed off into the ditch. When it finally started to clear we saw if we had backed up any further we would have run off into a lake."
Mr Hanes perhaps had a luckier escape still. When the worst duster of all struck on 14 April 1935 – Black Sunday as it became known – he, aged 11, and his father were driving tractors side by side in the fields. "The sky started to boil… we jumped into our pick-up. It got so dark I couldn't see him sitting next to me." With no daylight at all, the two of them followed a fence to a nearby barn and then later made it to their small house. "We got to the back door of the house and mum had everyone with wet rags over the faces. We knew we were well protected then."
Neither man can see a repeat of the Dust Bowl in all its agony – federal farm subsidies and the social safety net make hunger on that scale unimaginable now. But they do see dangerous patterns returning, both in the weather and in agricultural practices. Whereas the federal government has for decades paid farmers to put fields back down to grass to bind the soil down, farmers who are putting profit over caution are now rushing to turn the sod over again.
If prices were to plummet, as they did at the start of the Depression, the land would once again be bare and vulnerable.
"I am worried," Mr Hanes concedes gravely. "If you just drive along you can see how they are just ploughing up grass everywhere. When the drought comes and the land is open like that it is going be subject to wind erosion again. If you get one field blowing, that accumulates on another and then it just keeps advancing."
At the No Man's Land Museum in Goodwell, 30 miles southeast of Keyes, which houses photographs and artefacts from the Dust Bowl days, Sue Weissinger, the director, says it is the failure of rain-starved Midwestern crops this year that is pushing up prices and thus driving farmers to speed up cultivation.
She too hears alarm bells. "I am afraid that they are going to rush to plant more around here. More and more land is getting ploughed up and that increases the danger that we will go back. I see that happening and that is exactly what happened in the Dust Bowl days."
In the museum we discuss where global warming fits in to this year's weather and wonder, if it worsens, whether it could also push all the southern Plains back to Dust Bowl conditions? Ms Weissinger flinches but then nods. "I do think it points to global warming, but that is not a point of view that is popular around here. A lot of people don't want to believe it." That reluctance is not just political, she adds, but born directly from the memories of the Dust Bowl.
"A lot of the old people here will still tell you that they were not at fault. It's hard for them to take responsibility."
Back in Keyes, however, Huston Hanes says it is time to recognise man's impact on the climate. "I don't think there is any question that we are affecting the weather patterns," he says. "Our weather is changing. We don't get rains any more like we used to and we don't get snows like we used to. So something has changed."
Mr Hanes doesn't expect it in his lifetime, but a time might come when the dust drops from the Panhandle sky all over again.
7,000 people moved out of the regions affected.
2.5m people moved out of the regions affected.
75% of topsoil was lost by the end of the 1930s.
100,000,000 acres of land was affected by the dust storms.
500,000 Americans were left homeless