Behind the Forecast: Outwitting the weather when baking

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Science Behind the Forecast 2/15/19

LOUISVILLE, KY (WAVE) - This topic is near and dear to my heart. I love to bake and avid bakers know that the weather can have a big impact on how sweet treats and savory temptations turn out. High humidity is often blamed for soggy pie crusts and deflating cakes but air pressure also has an impact.

The National Weather Service defines relative humidity as

“A dimensionless ratio, expressed in percent, of the amount of atmospheric moisture present relative to the amount that would be present if the air were saturated. Since the latter amount is dependent on temperature, relative humidity is a function of both moisture content and temperature. As such, relative humidity by itself does not directly indicate the actual amount of atmospheric moisture present.”

So in layman’s terms, relative humidity describes the amount of water vapor in the air compared to the total amount of vapor that the air can hold at a particular temperature. Warmer air can hold more moisture than colder air. That means, even with the exact same amount of water vapor in the atmosphere, there will be a higher relative humidity if the air is cooler than if it was warmer. When meteorologists mention humidity on air, typically we’re describing the relative humidity.

Since warmer air can hold more water vapor, bakers typically run into more issues on those warmer and rainy days. The extra moisture soaks into dry ingredients quite easily. Bakers can fight the higher humidity by extending the baking time in five minute intervals. Also reducing the amount of liquid in a recipe is always a good idea. It’s recommended that the amount of liquid is reduced by one-quarter. If the batter is too dry once mixed, then the additional liquid can be added back in.

Another way to fight high humidity, store dry ingredients in a refrigerator or freezer. This keeps them fresher but they must return to room temperature before use or cakes and breads will not rise properly.


Atmospheric pressure also impacts how baked goods turn out. If an area of low pressure is nearby (think cold fronts) then cakes will act as if they are being baked at a higher altitude, where air pressure is also lower.

Water boils when as the heat rises, pressure inside the water becomes greater than the pressure outside the water. Lower air pressure leads to lower boiling temperatures of water. Water boils at about 212°F at sea level but about 200°F at 6,000 ft. Since the water boils at a lower temperatures when there's lower air pressure that means more water evaporates before the baking process is complete. Also since there's less atmospheric pressure, cakes and breads typically rise more quickly.

Avoid deflating cakes by reducing leavening agents such as baking powder and baking soda. Reduce baking powder by half a teaspoon or baking soda by a quarter teaspoon to limit the cake rise.

Adding two to three tablespoons of flour or a half beaten egg white to a cake batter traps the gas from leavening process which keeps the cake from deflating.

Hopefully checking the forecast before the next time you channel your inner Betty Crocker may help prevent a baking disaster.

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