There’s hot, like the typical heat of summer when children’s popsicles melt down their wrists before they can eat the whole thing, and the cool water from the garden hose is perfect to wipe away sweat and sticky dribbles. Then there’s HOT, like the soul-wilting swelter that makes people sick just walking around, mowing their lawns, or playing a little pickup basketball.

Heat is the #1 weather killer in America. Heat kills more Americans than tornadoes, hurricanes, flooding, lightning, cold, snow, and rip tides. Many of the heat deaths are preventable with attainable safety steps, such as providing cooling for vulnerable people who do not have air conditioning, moving sports practices indoors or canceling them altogether, and ensuring people (especially children) are not left inside parked cars.

June has been a hot month in many parts of the U.S., and it’s only going to get worse. It isn’t just a typical summer heat, but rather extreme summer temperatures — the dangerous kind that causes illnesses and deaths. You probably have heard about the heat wave already and don’t need me to rub it in. Instead, I’m here to show you how to see it coming more than a few days in advance.

Heat is one of the most predictable of dangerous weather types. Forecasters often can detect an imminent heat wave 2–3 weeks in advance. They translate their computer models and statistics into maps that anyone can access, if you know where to find them and how to read them. Let’s break these down.

1. Climate Prediction Center’s 8- to 14-Day Temperature Outlooks*

In the world of “extended-range” climate outlooks (that is, around 8 to 28 days out), forecasters don’t point to a specific temperature as a target in their forecasts. Instead, they predict the chances that temperatures will fall into one of three categories: above normal, near normal, and below normal. The basis for comparison that defines “normal” is the 30-year period of 1981–2010. Based on those years, the three categories divide the temperatures into thirds — that is, one-third of the years in the comparison period fell into each category. A forecast of “climatology” would indicate an equal chance of each category — a 33.3% chance, to be specific. Any change in the chance of any category indicates that forecasters see something in the models and statistics that nudge them to tilt the odds. A weak signal results in a slight shift — maybe a 40% chance of temperatures in the above-normal category instead of a 33% chance. A strong signal can push those chances to 70%, 80%, even 90%.

The Climate Prediction Center’s 8- to 14-Day Temperature Outlook issued on June 17 for June 25-July 1, 2022. Pie charts show the chances for above-, near-, and below-normal temperatures in the location at the tip of the arrow. You can find these outlooks updated daily at https://www.cpc.ncep.noaa.gov/products/predictions/814day/interactive/index.php and https://www.cpc.ncep.noaa.gov/products/predictions/814day/

On June 17, the chance of temperatures in the above-normal category for Days 8–14 (June 25–July 1) is as high as 70–80%. In other words, temperatures like the warmest third of normal are very likely — almost as high as confidence can get at that range. (For what it’s worth, the 6- to 10-day outlook has above 90% confidence in the same area, with the extra boost of confidence that comes with being closer to the dates.)

Pie charts are a brilliant way to show how the chances for each category change as the odds tilt more strongly. Each increase in the chance comes with a much bigger piece of the pie. The other categories are never impossible, but they sure do become a lot less likely.

It’s important to remember that the outlook is for the entire Week 2, averaged together. If the first few days of that week are likely to be in the above-normal category, but the rest of the week swings to the below-normal category, the result will be much closer to near-normal for the whole week together. Even with a strong tilt in the odds, it’s possible that not every day in the period will be in the above-normal category. We have to dig deeper for information about the timing of the heat.

*The Climate Prediction Center also produces 6- to 10-Day Outlooks, which are translated similarly. We’ll focus on 8- to 14-day outlooks here for simplicity.

2. Climate Prediction Center’s 8- to 14-Day Extreme Temperature Outlook

The Climate Prediction Center’s hazards outlooks for days 8–14 highlight parts of the U.S. with slight (20%), moderate (40%), or high (60%) chance for extremes in temperatures, precipitation, wind, and snow. They define “extreme” temperatures as the warmest (or coldest) 15% for the time period of interest AND high temperatures above 90 degrees, or low temperatures above 80 degrees. Unlike the temperature outlook, the Climate Prediction Center often narrows the date range to just a few days within the 8- to 14-day period. A moderate or high risk of excessive heat is a warning alarm that a heat wave is coming. Even a slight risk bears watching as the days approach. The high risks, though, indicate the highest level of warning forecasters can give for something that’s over a week away.

The Climate Prediction Center’s 8- to 14-Day Hazards Outlook for temperatures issued on June 17 for June 25-July 1, 2022. You can find these outlooks updated every weekday at https://www.cpc.ncep.noaa.gov/products/predictions/threats/threats.php

A meteorologist can take that “warmest 15%” label and translate it to numbers for their own areas of interest. They can pull the climate record and find the threshold for the warmest 15% of temperatures. For example, in the 123 years of records at Dallas/Ft. Worth for June 25–27, the maximum temperatures for the warmest 15% are 98 degrees or greater.

3. Dig Deeper!

If you like what you see, there is even more information available from the Climate Prediction Center! For more information on understanding these outlooks, you can take the very same training that’s available to the National Weather Service’s meteorologists.

Oh, and don’t forget your own heat safety measures, especially because you have a lot of warning to prepare for it.

• Drink plenty of non-alcohol, non-caffeinated fluids.
• Stay in the shade or indoors as much as possible during the hottest time of day (typically mid to late afternoon). If you must be outdoors, take cooling breaks.
• Move exercise and sports practices indoors. You can try to move them to morning, but mornings during a heat wave are often hot, too, so be careful.
• Wear sunscreen.
• Check the backseat every time you leave your car parked. Do not leave children, vulnerable adults, or pets in parked cars.
• Know the symptoms of heatstroke and heat exhaustion, and take them seriously. Heatstroke is a medical emergency.

Drop a note in the comments if you need a hand breaking down the outlook for your area. I’m happy to help!