COLUMBUS, Ohio (WCMH) – As temperatures worldwide increase due to human-caused climate change, so do long stretches of hot days with little to no relief.

And in Columbus, those heat streaks have increased the most of any metropolitan center in Ohio, according to new research published this week by Climate Central.

The nonprofit organization’s analysis of temperature history for cities across the U.S. found Columbus is one of many places seeing longer heat streaks in the past 50 years. Here in Ohio’s largest city, the longest yearly streaks of days at or above 80-, 85- and 90-degrees Fahrenheit have risen since 1970.

Although the lines on the graphs above zig and zag, they show upward trends. And the highest of high heat streaks have happened more recently, as the longest heat streaks above each degree threshold have happened in the past 10 years:

  • 45 straight days above 80 degrees in 2011
  • 26 straight days above 85 degrees in 2019
  • 12 straight days above 90 degrees in 2020 (tied with 1999)

“At that point, it becomes more than an inconvenience,” said NBC4 meteorologist Liz McGiffin. “You just expect it to be hot when you hit the end of July, beginning of August. And that’s when you start to even reach a point where it could be hazardous to your health and really just more than just an inconvenience.”

Nationwide problem with local implications

Columbus saw the biggest increase in heat streak days among the 10 Ohio cities Climate Central analyzed. Nationwide, 190 of the 246 U.S. cities in the study (77%) are experiencing longer stretches of extreme heat compared to 50 years ago.

And extremes do more damage to places with naturally high summer heat.

Phoenix, for example, saw six straight days in June above 115 degrees Fahrenheit, its longest on record. The previous record, four consecutive days, was set twice in 2020. Longer heat streaks also hurt western cities currently experiencing a decades-long megadrought.

Extreme heat days, especially during the dog days of summer, can be worsened by humidity. It’s that combination that bumps up the heat index and causes heat advisories like what Columbus saw earlier this month when it felt like 100 degrees or more on some 90-degree days.

Heat index chart via National Weather Service

“There’s a lot of times that people can shrug off, ‘Eh, it’s a day or two in a dry heat,’” McGiffin said. “But as soon as you get that oppressive humidity in there – and as soon as you have temperatures that are too hot to even go out by the pool – that’s when you start hitting a danger zone.”

In a naturally milder climate like Ohio, McGiffin said, elongated dangerous heat can take a toll on outdoor workers not used to the temperatures.

“Those are people who have to adjust their schedules and can be the most at risk for some of those health hazards,” she said.

But longer heat streaks can also show their effects in more subtle ways.

“You’ll notice maybe the flowers start to bloom a little earlier, and then they stay in bloom a little later,” McGiffin said.

The top 10 cities in Climate Central’s analysis with the longest increases in heat streak days all increased by more than 10 days. Eight of those cities were in Texas, and the other two were Miami and Lake Charles, Louisiana.