Wednesday's expected high temperature in Charlotte of 94 degrees is 5 degrees above normal — and part of a decades-long trend toward more hot days in summer.
In 1970, Charlotte saw about 47 summer days with average temperatures above normal, the independent research organization Climate Central reported. In 2017, the city experienced 64 such days.
Unusually hot days in Raleigh-Durham more than doubled, from about 24 days in 1970 to 59 last year.
Summers are growing warmer in most U.S. cities as increasing amounts of greenhouse gases such as carbon dioxide add heat to the atmosphere, Climate Central says. More than 90 percent of the 244 cities it analyzed saw a rising trend of summer days above normal — average daily temperatures from 1981-2010 — over the past half-century.
Charlotte's six warmest summers since 1878 have all occurred since 1986, the National Weather Service reports. It's seen temperatures of 90 degrees or higher on eight days this month and 19 days in June.
Forecasters expect warmer-than-normal temperatures in July, August and September across the Carolinas.
The rising heat puts more people at risk from heat exhaustion and the more serious heat stroke, especially older ones, health experts say.
North Carolina Health News cited a national study that found people between 65 and 74 run a 5-percent greater risk of death during heat waves. People 75 and older have an 8.2-percent increased risk.
More than 1,600 heat-related illnesses have already been reported by North Carolina emergency departments this summer, the N.C. Department of Health and Human Services says. A 2012 heat wave, in which Charlotte reached a record 104 degrees, killed at least 82 people nationwide.
The department has this advice for staying safe during hot weather:
- Increase fluid intake.
- Spend time in cool or air-conditioned places.
- Reduce normal activity levels.
- Talk with your doctor if you take medications that can impede heat loss, such as for high blood pressure, allergies or muscle spasms.