Days when the temperature breaks 100 degrees Fahrenheit at U.S. military bases will happen by 2050 nearly five times as often as they do now without action to address climate change, the Union of Concerned Scientists said in a report released Monday.

All told, it will amount to roughly another month of dangerous heat every year, according to the nonprofit group. Unsurprisingly, troops at bases in the Southwest and the South will suffer more than peers elsewhere, including the Marine Corps Air Station in Yuma, Ariz. and the MacDill and Homestead bases in Florida, which are forecast to be the three facilities that see the greatest increases.

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“The three hottest bases by midcentury,” Kristy Dahl, the lead author, said in a statement, “would each experience the equivalent of nearly four months per year with a heat index over 100 degrees Fahrenheit.”

The term “heat index” blends temperature and humidity to describe to what it feels like outside.

Coupled with statistics from the Pentagon, the research underscores the significant physical dangers climate change poses to the U.S. military, such as flooding threats to island installations, infections from tropical diseases and forest fires set off from live-fire drills.

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UCS researchers studied 169 “major” military installations, places with more than 1,000 people, and excluded Coast Guard and foreign facilities.

The rate of heat-related illnesses and injuries for American troops is rising in every branch of the armed services and is about 50 percent higher than it was just five years ago, new data from the Military Health System, a division of the Pentagon, show.

Government figures show about 40 percent of the nearly 2,800 heat-related illness cases from 2014 through 2018 occurred at five bases in the South: Fort Benning, Ga.; Fort Bragg, N.C.; Camp Lejeune and Cherry Point, N.C.; Fort Campbell, Ky.; and Fort Polk, La.

At least 17 people have died of heat exposure while training at U.S. military bases since 2008, according to the Pentagon. And younger recruits and recruits from northern states are more likely to succumb to heat illnesses.

As a recent report from the Armed Forces Health Surveillance Branch put it: “Although numerous effective countermeasures are available, heat-related illness remains a significant threat to the health and operational effectiveness of military members and their units and accounts for considerable morbidity, particularly during recruit training in the U.S. military.”

Unless greenhouse gas emission levels slow rapidly and significantly, troops nationwide will sweat through dozens more 100-plus degree days.

Homestead, the Air Force base in Florida, would go from 13 extreme heat days on average, to 115 annually by mid-century, for example. Even installations in northern states would see dozens more 100-plus-degree days. Delaware’s Dover Air Force Base and Maryland’s Andrews Air Force Base are on track for more than a month of extreme heat days — a stark change from conditions now, when they experience an average of less than a week of such days.

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The military has seen an increase in so-called “black flag” days, when training exercises are called off due to unsafe conditions, such as heat.

“Last year, drills had to be rescheduled because of dangerous heat conditions,” Shana Udvardy, another UCS researcher who worked on the study, said. “But how do you reschedule around the entire summer in the decades ahead?”