The rule would be aimed at mail carriers, delivery people, construction workers, landscapers, restaurant staff and others exposed to consistently high heat indexes, which measures how the temperature actually feels to humans.
The measure -- which would affect about 35 million workers, according to the government -- would apply to those working both inside or outside who can expect to be exposed to a heat index of 80 degrees Fahrenheit (26 Celsius) or higher.
"The purpose of this rule... is to significantly reduce the number of worker-related deaths, injuries and illnesses suffered by workers who are exposed to excessive heat... simply by doing their jobs," a senior administration official told reporters.
Under the rule, employers would be required to develop heat injury and illness prevention plans, and appoint a workplace heat safety coordinator.
If the heat index were to hit the 80-degree mark, workers would have to be provided with drinking water and access to break areas in the shade or in air-conditioned spaces.
Measures also would have to be implemented to allow for the "acclimatization" of employees who are either new or returning to work after illness, including more frequent breaks and a reduced workload until employees are back up to speed.
"Three out of four workers who die on the job" due to heat-related illnesses "die in that first week on the job," the official said.
The rule, if finalized after a period for public debate, would be the first such rule in the United States at the federal level.
If the heat index were to exceed 90 degrees Fahrenheit, all employees would be allowed a 15-minute break every two hours, and managers would be required to monitor their workers for symptoms of heat-related illnesses.
Some workers, such as emergency medical personnel, would not be subject to the new rule.
The announcement, which comes as summer sets in across the United States, is one of a series of measures unveiled Tuesday by the Biden administration concerning extreme heat.
But the new work rule could be scrapped by a new administration should Biden not be reelected in November.
