Weather data show humidity has dropped across US since 1995. What it could mean.
AI-generated summary reviewed by our newsroom.
- US humidity fell 5.3% since 1995 while temperatures rose ~0.5°F per decade.
- Dew point rose modestly before 1995; rainfall fell 2.7% while heavy storms rose.
- Lower humidity can raise drought and fire risk; heavy downpours boost flood risk.
As average temperatures have climbed in the U.S. due to climate change, relative humidity has dropped, a change that could have big impacts in different parts of the country, an AccuWeather study shows.
For the study researchers entered decades of nationwide weather data to search for statistically significant climate trends. They found:
- Across the United States, temperatures have increased an average of about a half-degree Fahrenheit per decade over the past 70 years;
- Dew point temperatures have climbed about three-tenths of a degree per decade over the same period, though the most notable increase happened before 1995;
- Relative humidity held mostly steady until 1995, then it began dropping. In the past three decades, it has fallen by 5.3%, or an average of 1.7% per decade;
- Average rainfall nationwide has dropped 2.7% since 1995, about nine-tenths of a percentage point per decade;
- The frequency of heavy rainfall — more than 4 inches in 24 hours — has increased by 70%. The frequency of rainfall events dropping more than 2 inches of rain in 24 hours have increased by 23% nationwide.
Joel Myers, who led the study for AccuWeather, wrote in a release about the findings that average temperature and dew point increased together in the U.S. until 1995, so the average relative humidity held more or less constant. But since 1995, the average temperature continued to increase while the dew point leveled off, causing the drop in relative humidity.
Dew point — that mystical figure that shows up in forecasts — is a measure of how much moisture is in the atmosphere. The National Oceanic and Atmospheric Administration says it’s the temperature to which the air must be cooled in order to reach saturation, or 100% humidity.
That doesn’t necessarily mean it’s raining, only that the air has reached the temperature at which it can hold the most moisture possible.
AccuWeather senior meteorologist Brett Anderson said in an interview that decreasing humidity over time has caused the decrease in rainfall. It’s also partly to blame for the heavier downpours when it does rain.
Because it’s an average, the national trend of less rainfall and heavier downpours won’t play out the same in every part of the country, causing different problems in different places, Anderson said.
As the Southwest and the western U.S. get drier, the region could see more frequent and more severe droughts, water shortages and worsening wildfires, forecasters say.
What do these trends mean for North Carolina?
If the climate continues to warm and humidity levels keep dropping, Anderson said the biggest concern for North and South Carolina would be extreme rain events.
Low humidity means less moisture at the ground level, but the moisture is still present, it’s just higher in the atmosphere, Anderson said, waiting for the right conditions to make it fall.
As the atmosphere warms up it can hold that much more moisture, he said. “Then that gets released in hurricanes or even thunderstorms. So instead of being spread out, more and more rain will come in shorter bursts.”
North Carolina has seen some catastrophic results from sudden excessive rain, most recently in the flooding from Tropical Storm Chantal and the remnants of Hurricane Helene.
Combined with sea level rise, more extreme rainfall events could mean more flooding along the coast, but also flash flooding in urban areas where there are more paved surfaces.
“And farmers don’t want that either,” Anderson said. “They like the rain more spread out.”
Climate scientists agree that average temperatures around the globe are rising, though not all believe the main cause is human activity.
“Obviously we need to reduce greenhouse gas emissions,” Anderson said. “That’s a worldwide thing, and we have not done that. Until we do, we’re going to continue to warm at a fairly steady rate.”
This story is available free to all readers thanks to financial support from the Hartfield Foundation and Green South Foundation, in partnership with Journalism Funding Partners, as part of an independent journalism fellowship program. The N&O maintains full editorial control of the work. If you would like to help support local journalism, please consider a digital subscription, which you can get here.
This story was originally published January 12, 2026 at 8:00 AM with the headline "Weather data show humidity has dropped across US since 1995. What it could mean.."
