Does having an extreme climate increase quality when aging bourbon?

Question

I've heard the claim that the state of Kentucky produces some of the best bourbons because the state's climate has dramatic temperature changes between seasons.

Kentucky has four different seasons with an invigorating climate. Summers are hot, wet, and humid. High temperatures repeatedly cross the 95°F (35°C) mark during peak summer in July, and the heat is oppressive. Winters are cold, but short of bitter, with night temperatures below 23°F (-5°C) in January. -Weather Atlas

The idea is that the wood in the barrel expands from the heat of summer, allowing the bourbon to penetrate deeper into the oak charred barrel wood... and then shrinks again during winter, pushing the liquid out of the wood again. I assume that most bourbon is stored indoors, so I have my doubts that the climate would have much effect, if any.

Is there any proof that having an extreme climate increases quality when aging bourbon?

Answer 1

The weather and climate definitly has an effect on how the whisky ages. But I wouldn't talk about increased quality. Quality in terms of "tastes better" is always something subjective. Some people prefer mildly aged spirits from scotland, some like in-your-face-oak from Texas (and some, like me, love both).

In scotland, the average temperatures only various 10°C on average. Whereas in traditional bourbon states like Kentucky it is four times as high. This leads to much more oak influence in the spirit, as you already wrote in your question, because the cask "breathes" (expanding and shrinking of the wood) more. Storing it indoor actually supports this effect, since those warehouses accumulate the heat. They are not air conditioned to a nice, cosy, constant temperature, but they amplify the outside temperature. Pretty much the same way a parking car in the sun get hotter inside, than it is outside:

Some distilleries even use containers to store their spirit, which pretty much cooks their bourbon (usually closed, only open for the photo):

...that's why they put it on the label, as well: