Millions of people across the central and eastern U.S. will experience scorching temperatures this holiday weekend. Stagnant high-pressure heat is expected to last several days.
In Oklahoma, temperatures will likely peak on Saturday, July 4. The Oklahoma City area is forecast to reach 101 degrees with a 105-degree heat index. Tulsa could be in the upper 90s with a 109 heat index.
Max Ungar, a meteorologist with the National Weather Service in Norman, said eastern Oklahoma will probably feel a few degrees hotter than other parts of the state.
"That's actually been driven by a lot of the recent rainfall we've had — really high rainfall totals northeast of Oklahoma City towards Tulsa," he said. "That's driving up the humidity, which combined with temperatures in the upper 90s to near 100 is boosting the heat indices."
Oklahoma temperatures are expected to stay in the 90s at least into next week. Public libraries, grocery stores and community centers can provide places to cool off and avoid overheating.
Researchers say heat waves are more frequent and lasting longer on average as humans continue to burn fossil fuels, trapping heat in the atmosphere. Zachary Labe, a scientist with research organization Climate Central, said in a recent article that climate change is accelerating extreme heat.
"Science shows that while summer heat is nothing new, climate change is pushing it beyond what we've experienced in the past," Labe wrote. "That includes hotter and more humid nights like those this week, which raise health risks because the body has less time to cool down and recover."
Is El Niño to blame for this heat?
Officials with the National Oceanic and Atmospheric Administration in June announced the arrival of El Niño, a naturally occurring weather pattern caused by weakening trade winds. Forecasters predict a particularly strong cycle, leading to what could be a "super" El Niño event.
But it's unlikely that the weather phenomenon is contributing to the blistering temperatures. El Niño mostly drives long-term seasonal changes, Ungar said.
" The small-scale, weekly even, weather patterns, they're not driven necessarily by the big climate forcers like El Niño," he said. "A lot of the heat this weekend is due to development of an upper ridge of high pressure."
" The heat we've had, the heat we've had for the several days, we will have for the next couple of days at least into the holiday weekend, is not directly attributable to those large-scale climate forcers."
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