Erika Spanger-Siegfried
Director of Strategic Climate Analytics

It’s the heart of summer and we expect it to be hot. But not like this.

Kristy Dahl

Kristina Dahl co-authored this report. She is a senior climate scientist for the Climate & Energy program at the Union of Concerned Scientists.

Extreme heat and humidity are forecast to smother much of the lower 48 states this weekend, Friday through Sunday. Depending on where you are in the US, it may have already arrived.

In the coming days, DC is expected to feel as hot as Death Valley; Philadelphia has declared a full-blown heat-health emergency; and temperatures up to 20ºF above normal for this time of year are likely to break all-time records across the country. With nighttime temperatures expected to hover around 80ºF, many places will have little hope of relief until the weather pattern breaks.

Staying safe in the face of this brutal heat will mean having to adjust our daily lives and our approach to the outdoors for a few days. But this heat wave is also like the ghost of summer future: it’s giving us an opportunity to pause, reflect on the new climate reality that we have created, and ask ourselves if the path we’re on leads to a future we want to live in.

As the temperature rises this weekend, here are three things we can do to ensure our safety now – and in the decades ahead:

  1. Plan wisely – including changing or scrapping your plans

It’s peak summer and lots of people have plans for the weekend, whether for work or play. Depending on the heat index forecast for where you are, you may need to change those plans. Developed by the National Weather Service (NWS), the heat index is “what the temperature feels like to the human body when relative humidity is combined with the air temperature.” And the heat index is going to be through the roof.

  • If you plan to be active: think twice. If your weekend involves working outdoors, playing sports, or exerting yourself in some other way, you could be at significant risk of heat illness. This is especially true for more northern parts of the country where people are less acclimated to the heat. (My two teen daughters have farm jobs and this week when the heat index (HI) rose well into the 90s here in Massachusetts, they both came home with heat exhaustion.) Many people who are scheduled to work outdoors this weekend will not have the option of doing otherwise. But employers and employees who can reschedule work should do so, and where this isn’t possible, they should be on the lookout for heat illness (see figure below) and take care to follow worker safety guidelines that include regular water breaks and access to shade. Download this workplace heat safety app developed by the Occupational Safety and Health Administration to get tailored safety reminders for the specific, real-time heat risk at your location.
  • If you plan to be in the sun: don’t. Many events scheduled for this weekend will be canceled or postponed because of the health risks. But if you’re planning to attend an outdoor event (think not just sports events, concerts, fairs and festivals, but also outings to public parks and pools, beaches and backyard gatherings), you may want to reconsider. The heat index gives you an idea of what it will feel like in the shade. But if you are in the direct sun, you could feel as much as 15 degrees hotter than the heat index forecast. And sunburn can also exacerbate heat stress.
  • If your plans include small children or elderly adults: proceed with great care. The heat index is forecast to top 100ºF in many places, which can be dangerous for anyone, but is especially dangerous for these people. E.g., kids often don’t read their bodies’ signals to rest and re-hydrate and elderly skin is less effective at sweating.
  • If you’re in the city: plan on it being hotter, including at night, because of the Urban Heat Island effect. The man-made material of the urban landscape (e.g., concrete, asphalt) absorbs excess heat on hot days and releases it at night, making city days and nights hotter than less urbanized areas. And on that note…
  • If you have plans at night: it will still be hot. One notable aspect of this heat wave is the failure of the nighttime low temperatures to drop low enough to provide relief. As Rich Giudice, executive director of Chicago’s Office of Emergency Management, warns “Even after the sun goes down, the temperatures will not drop much below 80 degrees, offering little to no relief.”

    Residents of New York’s Lower East Side neighborhood escape the heat in one of the city’s designated cooling centers in New York, Saturday, July 24, 2010. More than 190,000 New Yorkers have visited cooling centers since the summer’s first heat wave on June 28, the city said in a statement. (AP Photo/David Goldman)

  1. Treat extreme heat like it’s deadly (it is)

Heat is one of the top weather-related causes of death in the US, with an average of more than 600 deaths per year. To stay safe, it’s important to treat heat as the dangerous threat it is and stay informed and vigilant. For general guidelines, there are lots of resources to draw on, from the CDC, NWS, and others. And for location specific guidance, listen to your local weather forecaster, check your town website or call. Across the country, our phones are ringing with automated messages from emergency managers and other local officials. Listen and take note.

  • Locate the cooling resources you need: In a heatwave, you’ll need to drink more water than you think, so have it handy at all times. You’ll need shade, so stay indoors or carry an umbrella if you need to step out. And you’ll need access to cool temperatures. If you don’t have air conditioning at home or ready access to it, know where the nearest cooling center is and have a plan for how to get there. Calling 211 can help you locate the one nearest you. Some municipalities are providing transportation to the local cooling center. Calling one’s town government, including a police station, can also help track down this information.
  • Know what to do if the power goes out: heat waves drive up electricity use as demand for air conditioning spikes. High temperatures and increased electricity use can strain the power grid, and indeed, there are risks of power outages this weekend. If this happens and your AC goes down, you’ll need to get to the closest cooling center with backup power.  Many cooling centers are municipal buildings with generators for backup power, but not all are equipped, so you should confirm before making the trip.
  • Offer help: Your neighbors may not have access to AC, or people to check in on them. If you are able-bodied, be that person. The deadly 1995 Chicago heat wave became a profound tragedy with many elderly lives lost due simply to their isolation: no one stopped in to check on them and to help with their mounting heat stress. We can also watch out for strangers. My colleague, Dr. Adrienne Hollis, has been tweeting about the need to carry and hand out water during this extreme heat. Watch out for people on the street, people on the job, homeless people. Consider printing and handing out copies of this at-a-glance heat illness guide. [A link to the attached pdf] A deadly heat wave is a crisis and we need to watch out for each other.

  1. Don’t let dangerous heat become everyday heat

Nobody is going to enjoy this heat wave. While most of us will simply bear the heat, many people are going to be sickened by it, and it’s likely it will cost others their lives. The heat wave has already claimed two lives in Maryland and one in Arkansas. These are not sultry days of summer; they’re dangerous, even deadly days.

Our latest work, Killer Heat, was undertaken so we could all see the threat of many more such days coming. And they are coming by the dozens, even hundreds, in our lifetimes. Unless we slow them.

Consider how meteorologists’ descriptions of what we’re facing right now compare with the frequency and extent of equivalent conditions by midcentury if our global carbon emissions continue to rise:

  • “More than 150 million people in nearly 30 states were under a heat watch, warning or advisory on Thursday morning…” —CNN
    • Per the National Weather Service’s general national guidance that suggests issuing a heat advisory when the heat index exceeds 100ºF, by midcentury more than 150 million people across the US would be under a heat advisory for 30 or more days per year.
  • “Over the next few days, more than 85 percent of the lower 48’s population will see temperatures above 90ºF…” —CNN
    • By midcentury, more than 85 percent of the lower 48’s population would see a heat index above 90ºF for 30 or more days per year.
  • “A total of 290 million [people] will see high temperatures of at least 90 degrees at some point in the next week…” –USA Today, based on a tweet by meteorologist Ryan Maue
    • By midcentury, roughly this many people would see a heat index of at least 90ºF for 30 or more days per year.
  • “Heat wave expected to bake two-thirds of nation through weekend.” —NBC
    • More than two-thirds of the nation by population—roughly 220 million people—would be exposed each year to the equivalent of a week or more with a heat index above 105ºF by midcentury.
  • “Metro Detroit is looking at about a 109-degree heat index value [for Friday].” –Detroit Free Press
    • By midcentury, Detroit would see six days with a heat index above 105ºF in an average year.
  • In New York City, “the heat index…is forecast to reach close to 107 degrees Saturday.” –NBC News
    • By midcentury, New York City would see eight days with a heat index above 105ºF in an average year.
By mid-century (2036-2070) regions of the United States with little to no extreme heat in an average year would experience such heat on a regular basis. Heat conditions across the Southeast and Southern Great Plains regions are projected to become increasingly oppressive, with off-the-charts heat days happening an average of once or more annually.

By mid-century (2036-2070) regions of the United States with little to no extreme heat in an average year would experience such heat on a regular basis. Heat conditions across the Southeast and Southern Great Plains regions are projected to become increasingly oppressive, with off-the-charts heat days happening an average of once or more annually.

So this weekend, try stepping outside for a minute when the heat index tops 100 or 105 and ask: what would my world be like if it felt like this more than 30 days each year?

If we let global emissions continue to rise through the end of the century, the forecast for an average summer would be unrecognizable to people sweating through the summer’s heat. 180 million people facing more than a months’ worth of days with a heat index exceeding 105ºF. 120 million people exposed to more than 7 days’ worth of heat each year that actually exceeds the NWS heat index chart, feeling hotter than 127ºF, but how hot we can’t say because they’re literally off the charts. You get the idea.

Killer Heat shows that even in an optimistic scenario in which we cap future warming at 2ºC, the US is in store for substantially more heat than we’re used to. So we need to adjust to this reality. Read our report for details on solutions. But if fail to reduce emissions and let the world blow past that important 2ºC mark (3.6ºF), we’ll look back on heat waves like this weekend’s three sweltering days, even with all the dangers they bring, as child’s play.

Six-year-olds Justin Mosquera, left, and Luke Taylor, relaxing in a stream of water from a fire hydrant near the Boys and Girls Club in Bowling Green, Ky. July 21, 2011