On Tuesday, two-thirds of the U.S. began burning up, according to forecasters. The scorching temperatures will be with the Midwest and the East Coast until the beginning of next week. And just when people need air conditioning the most, some cities may soon see electricity outages.

Heat watches have been issued, and by Tuesday night, the National Weather Service had 34 million people under heat advisories. For the Eastern region, the former is issued when the heat index value could potentially reach at least 110 degrees, while the latter signals that the heat index value is expected to be between 105 and 109 degrees. The thresholds are slightly lower west of the Blue Ridge Mountains.

Temperatures are predicted to continue rising throughout the week, with the Midwest experiencing its hottest temperatures on Friday, and the East seeing the worst of it on Saturday or Sunday. According to the Washington Post, the coupling of high dew points—meaning stifling humidity—and soaring temperatures may result in elevated nighttime temperatures and could make this heat wave particularly dangerous to public health. In Philadelphia, Tuesday was declared a code orange ozone action day, signifying that ozone levels in the environment were dangerous for sensitive groups. Ozone levels can meet the criteria for code orange at any time of the year, but they’re often highest during heat waves, when high pressure and high temperatures result in elevated concentrations of ozone particles. The warning was downgraded by Wednesday but will likely rise back to “code orange” concentrations again by the weekend, according to the Environmental Protection Agency’s AirNow monitoring system.

In response, cities have started providing the usual recommendations to residents—drink plenty of water, stay out of the sun, try to spend as much time in the A/C as possible. To make it easier for residents to cool down, Philadelphia and New York are making all public pools free until further notice. New York is also offering spray showers in the park when temperatures reach 80 degrees or higher. In the Midwest, cities like Chicago and Detroit are also buckling down and will likely record their highest temperatures of the summer. The Windy City will offer residents six “cooling centers” located inside community service centers where they can beat the heat.

Mike Clendenin, the spokesman for Consolidated Edison, the company that operates New York’s power grid, told Pix11 news regarding the upcoming heat wave, “We do expect there to be power outages … with any heat wave, you’re going to have power outages. They happen. But our crews are ready to respond to anything.” The company’s statements follow the five-hour outage in Manhattan on Saturday, which was caused by equipment failure and was unrelated to the heat wave.

Systems around the country are bracing for impact, but if you think it seems logical that power outages will provide a brief reprieve for the environment, think again. Carl Pope, senior climate adviser to former New York City Mayor Michael Bloomberg, told USA Today that there are “all kinds of inefficiencies and waste” that only multiply during a blackout. For instance, we fall back on diesel generators when electrical grids go out, which magnifies the carbon footprint. Besides that, manufacturing processes that were halted during an outage have to be restarted after the power comes back on, resulting in a lot of wasted product.

The heat wave should end by Sunday, but until then, in some cities, utility companies have backup crews working extra hours to try to keep the lights on.

While a heat wave in the middle of July is not unexpected, events like this could become much more common within the next few years, thanks to climate change. This heat wave comes just a few weeks after a hellish rash of high temperatures in Europe, where air conditioning is much less common.