xkcd #3187: High Altitude Cooking Instructions
Title text:
1,300,000-1,400,000 ft: Ask a crew member to show you how to use the ISS food warmer.
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Source: https://xkcd.com/3187/
this post was submitted on 29 Dec 2025
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I used to live at 3300 feet. Cooking times increased slightly over what most recipes recommended, sometimes more baking powder was needed, but I don't remember having to add more water.
The higher altitude, the lower the atmospheric pressure, and the lower the boiling point of water. At 3300, you were down to 207°f. I used to work at a restaurant at 8k feet and we were down to a boiling point of 195, which was enough to make things like, say brownies, noticeable dryer if you didnt compensate for the extra water boiling off durrong cooking.
We actually had a fancy oven for pastry that you could set the pressure inside of, allowing us to cook things as though at sea level.
I don't know how much that is in the Boiling Water system
Meant to leave that context for for our metric friends, but my post was getting long so I shortened it. In Fahrenheit, water boils at 212°f and freezes at 32 at 1 atmosphere. (Sea level) the conversion rate is 1.8°f=°c (after subtracting those 32 'extra' degrees)
So at 207, his boiling point is only 5°f (3.33°c) lower than at sea level. Whereas where i was cooking, it was closer to 10°c - enough to considerably dry out anything baking for a decent amount of time, and throw a lot of baking chemistry off (anything leavening with baking soda, etc changes, and breads risk colapsing although that's less about the h2o, and more about the pressure iirc)
7k here, I really need to invest in a pressure cooker.
The extra cooking time results in more water loss. I'd imagine in most recipes it'd be nearly imperceptible.
Definitely not as much as half a cup.
Wouldn't it depend on how many cups the original recipe calls for?
I wonder if it's assuming you don't use a slightly lower heat output though despite the lower boiling point?
If you're cooking something at altitude you shouldn't lower the heat - you still need to cook it properly.
I'm not sure if it's still the case but most of the population in Mexico is above 3000 feet so recipes had variations for sea level instead (the recipe was made for 1000msnm)
Sometimes it was confusing if you got something imported from the US or some brand that needed to be adjusted for high altitude