Heat and Humidity
Week of June 29, 2025 – July 5, 2025
by Elizabeth Suzedell, Environmental Educator
A heat wave last week brought both high temperatures and high humidity to Central New York, making it feel as muggy and oppressive as the tropics. This weather got me thinking a lot about how heat and humidity create different climates around the country.
Humidity is the measurement of the amount of water vapor in the air. Our atmosphere is like a sponge- it can hold a certain amount of water vapor. If the atmosphere, or “sponge,” is half saturated with water vapor, then the relative humidity is 50%. If it is completely saturated with water vapor, then the relative humidity is 100%. At that point, the atmosphere cannot hold more water vapor, so it starts to condense into liquid water, creating fog or rain.
Another useful way to think about humidity is through the dew point, which is the temperature in which the air must be cooled to in order for water vapor to condense. Last week, Central New York had very high dew points around 75°F, which is typical of Florida’s climate. In contrast, lower dew points mean drier conditions. This weekend in Tucson, Arizona, dew points are only around 40°F. With temperatures there reaching over 100°F, the relative humidity is less than 15%!
When it gets too hot and we start to sweat, water evaporates from our skin. For water to make this change from liquid to gas, it needs a boost of energy. So, when it evaporates, it takes a little bit of heat from our skin with it, cooling us off. However, during the heat wave last week, did sweating actually help you that much? This evaporative cooling isn’t as effective in humid environments because the air is already so saturated with moisture. In Arizona, where the air is extremely dry, water evaporates quickly, so sweating actually works.
Where would you rather spend a day- hot and humid subtropical Florida, or extremely hot, but dry, desert Arizona?
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