It’s the heat AND the humidity: OHIO’s Ryan Fogt discusses record-breaking mugginess of June and July

Ohio University Professor of Meteorology Ryan Fogt, Ph.D., is a climatologist with expertise in climate change, weather events and the variability and dynamics of large-scale climate in the Southern Hemisphere. He also serves as Director of OHIO’s Scalia Laboratory for Atmospheric Analysis. Fogt says that short term changes in conditions like humidity are typically associated with weather patterns.

“In the short term—weeks to months—[high humidity] is tied to weather patterns, and whether or not the air above us is sourced from a large, warm body of water,” said Fogt. “If we continue to be in a pattern where the air above us is sourced from an ocean—particularly a warm ocean like the western Atlantic Ocean or the Gulf of Mexico—the dew point temperature can remain high.”

If a persistent weather pattern sets up and continues to supply air from these regions to the eastern U.S., the humidity will continue to be much higher.  This was the case this summer for most of the U.S. east of the Mississippi River. Due to a persistent large-scale atmospheric pattern, there were not many days of below average temperatures in June and July.

When patterns emerge over a longer period of time, Fogt says there is a stronger chance that extreme conditions, like the excessive humidity of this summer, are indicative of climate change.

“In the long term—years to decades—the increase [in humidity] likely would have a background climate change signal,” he said. “There is a possible long-term climate change here. As the air warms from greenhouse gas increases, it theoretically can also hold more moisture, giving rise to higher dew points if the air is sourced from a large moisture source [like the ocean].”

Higher dew points are certainly something that many parts of the eastern U.S. have experienced this summer. Dew point is the temperature at which air reaches saturation (the most water vapor it can hold), and when dew will start to form on surfaces, according to Fogt. Unusually high dew points are indicative of extreme humidity. In June and July, the average dew point was more than 6°F higher than normal in many major cities. Columbus, for example, had an average dew point that was 6.2°F higher than normal.