LAUSR

The population of the southeastern USA is exposed to frequent extreme summertime high heat and humidity and is thus vulnerable to the resulting human thermal stress. Regional dew point variability in the USA is relatively underexplored in the literature compared to extreme heat. Here, we analyze hourly summer dew point data from 34 cities in the region during the period 1973–2022 (n = 50) to identify annual values of extreme dew point hours (EDH) and extreme dew point days (EDD). Regionally, significant (p ≤ 0.05) positive trends for both EDH (rs = 0.28, R2 = 0.078, +1.53 EDH/year) and EDD (rs = 0.30, R2 = 0.086, +0.05 EDD/year) occurred, although not all stations had increased dew point temperatures. Rather, positive changes are most concentrated among stations located along the upper Piedmont of the southern Appalachian Mountains. Conversely, no significant (i.e., p < 0.05) differences in either aggregate mean values of EDH or EDD occurred when splitting the data into early (1973–1997) and late (1998–2022) periods. High summer values of EDH and EDD are associated with variability in the 500 hPa geopotential height flow over North America. In particular, anomalous high pressure over the Gulf of Alaska is associated with the highest frequencies of summer extreme dew points in the study area, and vice versa. This connection to slow-changing ocean–atmosphere variability could lead to enhanced predictability of periods of extreme high dew point conditions in the Southeast, with implications for human well-being.