Dewpoints, as mentioned above by BrianK, are a better measure of humidity than percent humidity, because the latter depends on the air temperature. The warmer the air, the more humidity it can hold, so hotter air with X percent humidity is a lot more humid than cooler air with the same percent humidity.
The dewpoint is the temperature at which the same amount of moisture in the air would be 100 percent humidity. When dewpoints reach the mid to upper sixties, most people feel uncomfortable from the humidity. This range is common in much of the northern part of the country (Chicago, New York, etc). It is highly unusual for dewpoints to reach the mid-seventies up north; that's the level of humidity commonly experienced in New Orleans and the rest of the Gulf Coast. But dewpoints of 75 have been experienced on and off over the past few weeks in much of the Midwest (including Chicago) and the Northeast (including New York/New Jersey).