On 29 June, as the so-called heat dome settled over British Columbia, Washington, and Oregon, the weather station near the Red Mountain AVA of Washington recorded an ambient temperature of 117.8 °F/47.7 °C. That was the third of what would be four days of high temperatures above 112 °F/44 °C which came hard on the heels of more than a week of highs above 95 °F/35 °C. Since then the daytime highs have not fallen below 97.7 °F/36.5 °C. Temperatures are expected to climb higher still in the coming days.

As untold billions of shoreline molluscs literally cooked in their shells, hundreds of people died from heat exhaustion, and scientists were presented with incontrovertible evidence that human-caused climate change bore responsibility for the heat, like many I found myself wondering just how the wine grapes were doing under the broiler.

‘I was pretty scared at first’, said Dick Boushey, who farms 300 acres (121 ha) in Washington’s Yakima Valley and manages another 300 acres of vineyards in the Red Mountain AVA. ‘But now, in the second week of this heat, I’m feeling a little bit better.’

Water was the primary determining factor for how vines weathered the heat, especially in the sandy, fast-draining soils of the Yakima Valley.

Boushey and his crews began irrigating in advance of the heat, and essentially they haven’t stopped since. ‘Perhaps counter-intuitively, I’ve also been putting on more compost, trying to get more organic matter into the soils, which should help with water-holding capacity’, said Boushey. While the water and the fertiliser are driving more vigorous growth in the vines than Boushey would want at this point in the growing season, that’s a trade-off he’s willing to make if it means he can avoid more serious losses. Nonetheless, he hasn’t got through the heat event scot-free.

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