Humidity and comfort explained: Why dew point matters more than relative humidity
Dew point, not relative humidity, tells you how muggy air feels: it is the temperature at which the air's moisture would condense. 59 of 138 large U.S. cities with NOAA hourly normals average a summer dew point of 65°F or more, led by Brownsville, TX (74.7°F).
First published · revised
Relative humidity versus dew point
Relative humidity swings through the day: NOAA's hourly normals put most cities' summer humidity near 80-90% at dawn and 40-60% in the afternoon, while the dew point barely moves. That is why the dew point is the steadier guide to how a day will feel.
Where summers are muggy and where they are dry
The muggiest large cities by summer dew point: Brownsville, TX (75°F), Corpus Christi, TX (74°F), St. Petersburg, FL (74°F), Miami, FL (74°F), West Palm Beach, FL (74°F) and Beaumont, TX (74°F). The driest: Reno, NV (37°F), Lancaster, CA (41°F), Las Vegas, NV (41°F), Boise, ID (42°F), Spokane, WA (43°F) and Salt Lake City, UT (44°F).
The heat index
The National Weather Service's heat index combines temperature and humidity into how hot it feels in the shade. NOAA's hourly normals include it for first-order stations; month pages show the afternoon temperature, humidity and dew point together.
Questions
What is a comfortable dew point?
Under 55°F most people find dry and comfortable; 55-65°F noticeable; 65-70°F muggy; above 70°F oppressive. These are common guidance, not a NOAA standard.
Why does 50% humidity feel worse at 90°F than at 70°F?
Relative humidity is relative to what the air can hold, which rises with temperature: 50% at 90°F holds far more water (a dew point near 69°F) than 50% at 70°F (near 50°F).
Source: NOAA NCEI 1991-2020 hourly normals.