Are You Living in One of America’s 15 Sweatiest Cities?

As temperatures soar across the United States, a startling study by the Union of Concerned Scientists predicts that by mid-century, the number of days with a heat index above 105°F could quadruple.¹ This climate shift is already evident, with Climate Central reporting that some cities have seen dramatic increases in extreme heat days.

The rising temperatures aren’t just uncomfortable—they’re potentially deadly. The CDC reports that over 1,200 Americans die from extreme heat annually.² From coastal humidity to desert dry heat, here are America’s sweatiest cities.

1. Austin, Texas

Austin experiences one of the most severe urban heat island effects in the United States. A study by the University of Texas found that between 1993 and 2011, the average surface temperature in Austin increased by 8.5°F. ^(ref)

The city’s rapid growth has exacerbated this effect, with nearly 350,000 acres of forest area cleared for development between 1973 and 1998.

Austin’s central business district can be up to 10.8°F warmer than surrounding rural areas. The city aims to mitigate this by increasing its tree canopy coverage from the current 45% to 50%.

2. Atlanta, Georgia

Atlanta’s urban heat island effect is significant, with temperatures in the city averaging 6°F higher than surrounding rural areas. The city’s nickname, “Hotlanta,” is particularly apt during summer months when high temperatures and humidity create oppressive conditions.

While beneficial, Atlanta’s abundant green spaces also contribute to humidity levels. The urban heat island effect in Atlanta nearly doubled in intensity between 1975 and 2014.

3. Washington, D.C.

Washington, D.C.’s urban heat island effect is intensified by its location on the Potomac River, which adds to humidity levels. The city’s wide avenues and numerous monuments create heat-trapping urban canyons.

Temperature differences between the urban core and surrounding areas can reach up to 21°F. The city’s land area falls within “heat islands” – areas that are significantly warmer than their surroundings. These heat islands are often correlated with low-income neighborhoods and areas with less tree cover.

4. Dallas-Fort Worth, Texas

The Dallas-Fort Worth metroplex has one of the most severe urban heat island effects in the U.S. On average, about 35% of Dallas’s urban land area is covered in impervious surfaces.^(ref)

This results in downtown Dallas being up to 12°F warmer than surrounding rural areas. The region experiences long stretches of 90-plus-degree days, often feeling even hotter due to the heat index.

5. Charlotte, North Carolina

Charlotte’s urban heat island effect has been intensifying as the city rapidly grows. Temperature differences within the city can reach up to 10°F between the hottest and coolest areas.

Charlotte’s tree canopy, which currently covers about 45% of the city, plays a crucial role in mitigating the heat island effect. The city is working to preserve and increase this canopy, targeting low-income, low-canopy areas that often correlate with warmer temperatures due to the heat island effect.

6. Baltimore, Maryland

Charm City brings the heat in more ways than one. Baltimore’s position on the Chesapeake Bay contributes to its high humidity levels, creating a sticky atmosphere that clings to the skin.

Summer temperatures regularly reach the 90s, with the heat index often pushing into triple digits. The city’s row houses and abundance of concrete and asphalt amplify the urban heat island effect, making some neighborhoods feel even hotter.

7. Denver, Colorado

The Mile High City might seem unlikely for this list, but Denver’s high altitude and intense sun exposure earn it a spot among America’s sweatiest cities.

While temperatures may not soar as high as some other entries, the thin air and strong UV rays can quickly lead to dehydration and overheating. Denver averages over 300 days of sunshine per year, giving residents plenty of opportunities to work up a sweat.

8. West Palm Beach, Florida

West Palm Beach’s proximity to the Atlantic Ocean and the Everglades creates a perfect storm of heat and humidity. Summer temperatures consistently reach the high 80s and low 90s, but the near-constant humidity really turns up the heat index.

The city averages over 130 days per year with a heat index above 90°F, making air conditioning a necessity rather than a luxury. Despite the sweltering conditions, residents and tourists flock to the beautiful beaches and outdoor attractions, armed with sunscreen and plenty of water.

9. Houston, Texas

Houston’s proximity to the Gulf of Mexico means the air is often thick with moisture, creating a sauna-like atmosphere for much of the year. Summer temperatures regularly climb into the mid-90s, with the heat index frequently breaking 100°F.

The sprawling metropolis’s concrete jungle intensifies the urban heat island effect, making some areas feel even hotter.

10. Orlando, Florida

Orlando’s inland location means it misses out on the cooling sea breezes that other Florida cities enjoy, resulting in stifling heat and humidity. Summer temperatures often reach the mid-90s, with the heat index regularly pushing into triple digits.

The city’s numerous theme parks and attractions mean visitors and residents are often braving the heat for fun, armed with portable fans and cooling towels. Orlando averages over 100 days per year with temperatures at or above 90°F, giving everyone plenty of opportunities to work up a sweat.

11. New Orleans, Louisiana

New Orleans’ location near the Gulf of Mexico and the Mississippi River delta creates a perfect storm of heat and humidity. The city’s famous festivals and outdoor events often include misting tents and cooling stations to help revelers beat the heat.

Despite the sweltering conditions, the vibrant culture of New Orleans keeps residents and tourists out and about, sweating it out in style.

12. Miami, Florida

Miami’s tropical climate means high temperatures and humidity are the norm year-round. Summer highs often reach the low 90s, but the near-constant humidity makes it feel much hotter. The city’s proximity to the ocean provides some relief through sea breezes but also contributes to the muggy conditions.

Miami’s famous beaches and outdoor nightlife scene mean residents and visitors are often embracing the heat, with plenty of opportunities to cool off in the nearby Atlantic or in one of the city’s many pools.

13. Phoenix, Arizona

The Valley of the Sun lives up to its name, bringing dry heat to a whole new level. While Phoenix may lack the humidity of other cities on this list, its extreme temperatures more than makeup for it.

Summer highs regularly soar above 110°F, with pavement temperatures hot enough to fry an egg. The urban heat island effect intensifies these already scorching conditions, making downtown areas feel like a furnace.

14. Las Vegas, Nevada

Las Vegas’s desert location means extremely hot and dry conditions, with summer temperatures often breaking 110°F. The city’s famous Strip, with its neon lights and concrete expanses, creates a significant urban heat island effect, intensifying the already scorching temperatures.

Despite the heat, Vegas never stops, with visitors and residents braving the conditions to enjoy the city’s famous nightlife and attractions. Many casinos and hotels offer poolside amenities and indoor entertainment options to help beat the heat.

15. San Antonio, Texas

San Antonio rounds out our list with its steamy South Texas climate. Summer temperatures regularly climb into the high 90s, with plenty of days breaking 100°F. The city’s famous River Walk provides a slight respite from the heat, but also contributes to the humidity levels.

From the scorching deserts of Phoenix to the muggy streets of Miami, each city on our list presents its own unique challenge to staying cool. Whether it’s the dry heat of the Southwest or the sticky air of the Southeast, residents have adapted to their sweltering surroundings with ingenuity and resilience.

Source:

1. Union of Concerned Scientists
2. Centers for Disease Control and Prevention