Muggy temperatures breaking records this summer, particularly in regions East of the Rockies, causing discomfort for residents.
The Eastern United States has been grappling with an unprecedented increase in humidity levels this summer, particularly in key cities like Washington, Baltimore, and Pittsburgh[1][3]. This rise in humidity has led to more frequent and prolonged periods of uncomfortable, muggy conditions, with many locations recording a record number of days with dew points above 65°F and even reaching oppressive levels of 75°F or higher[1][3].
Climate change has contributed to this increase in humidity primarily by warming the atmosphere, which allows it to hold more moisture. Warmer air increases evaporation from water bodies and soil, causing higher water vapor content in the atmosphere, which intensifies humidity and fuels heavier precipitation events[4]. The frequent warmer temperatures in the Eastern US retain more moisture in the air, thus increasing mugginess at night and during summer days[1][3].
Additional factors influencing humidity increases in the broader Midwest and Eastern US include changes in land use, such as the expansion of agriculture (e.g., corn and soybean crops), which contributes water vapor through evapotranspiration, further elevating local humidity levels[2]. Natural variability, such as ocean temperature changes in the Pacific, may also modulate humidity trends but climate change is a significant underlying driver[2].
This elevated humidity combined with higher temperatures increases heat stress risks and has implications for human health, agriculture, and energy demand in the Eastern United States[1][3][4]. University of Georgia meteorology professor Marshall Shepherd stated that uncomfortable humidity is moving further north, into places where people are less used to it[5]. Summers now, according to Shepherd, "are not your grandparents' summers."
In the West, the situation remains much drier compared to the East and South. However, the summer of 2025 has seen dew points that average at least 6 degrees higher than the 1951-2020 normals in several cities, indicating a shift in humidity patterns[1][3]. Highs in the 90s are expected this week around the Puget Sound region during the Seattle heat wave[6].
| Aspect | Description | |-----------------------------|----------------------------------------------------------------------------------------------| | Humidity trend | Rising; record high summer dew points, more days with oppressive humidity | | Climate change contribution | Warmer atmosphere holds more moisture, increases evaporation and water vapor content | | Additional factors | Agricultural evapotranspiration, ocean temperature variability | | Impact | More frequent muggy, uncomfortable, and potentially dangerous heat conditions in the East |
References:
- NOAA - National Centers for Environmental Information
- National Climatic Data Center - Climate Change Signals
- National Oceanic and Atmospheric Administration - Climate.gov
- Environmental Protection Agency - Climate Change Indicators
- University of Georgia - Department of Geography
- The Seattle Times - Weather
- The weather in Seattle is expected to be hotter this week, with highs reaching the 90s during the Seattle heat wave.
- Climate change has significantly contributed to the rising humidity levels in the East, particularly in cities such as Seattle, by warming the atmosphere and increasing the water vapor content.
- Environmental-science studies indicate that warmer temperatures in the Eastern United States are retaining more moisture in the air, leading to an increase in mugginess at night and during summer days.
- The increased humidity combined with higher temperatures in the East has implications for human health, agriculture, and energy demand, as it creates more frequent and prolonged periods of uncomfortable, muggy conditions.
