Extreme heat is affecting workers this summer. New federal rules would require bosses to provide rest, water, and shade.

• The Biden administration proposed the first-ever national heat protection standards for workers.
• The rule targets about 35 million workers in industries like construction and agriculture.
• The proposal comes amid record heat waves exacerbated by the climate crisis.

The Biden administration on Tuesday proposed the first-ever national standards for protecting workers during excessive heat .

The rule, if finalized, would affect about 35 million workers across the country in industries like construction, agriculture, delivery, landscaping, and utility line repair. Workers in restaurants and factories where there isn't access to air conditioning could also be covered by new requirements for employers.

The Occupational Safety and Health Administration has to accept public comments before drafting a final regulation in the coming months. If finalized, Republican-led states and business groups are likely to sue the administration to block the rule, and a string of recent Supreme Court rulings curtailing federal agencies' power could also make it harder for regulations to survive legal challenges. Former president Donald Trump would likely block the rule from becoming final if he wins a second term in November.

The proposal comes as millions of indoor and outdoor workers have been exposed to record-setting heat waves this summer. On Tuesday, more than 75 million Americans were under heat alerts, according to the National Weather Service . The climate crisis is causing more frequent, intense, and longer-lasting heat waves in major cities across the US, federal climate scientists have found.

"Heat is a problem and a growing one," Acting Labor Secretary Julie Su told Business Insider. "For workers, it's not just inconvenient or uncomfortable, it's it's actually potentially deadly. So we are doing this because no worker should have to do a job that's life threatening."

More than 436 workers died on the job due to heat exposure between 2011 and 2021, according to the Bureau of Labor Statistics. Nearly 34,000 workers suffered heat-related injuries that required time away from work.

OSHA last year said these figures are "vast underestimates" because the definition of a heat-related illness varies by jurisdiction and there's a lack of recognition that heat is a "causal or contributing factor to illness." That leads to inconsistent reporting by medical professionals and employers also underreport these cases, OSHA said. The agency has been criticized by worker safety advocates for failing to conduct more heat inspections, as well.

What will employers have to do and when?

OSHA is proposing two heat index thresholds that kick in requirements for employers. The heat index is what the temperature feels like to the human body when humidity is combined with the air temperature.

Employers with workers exposed to 80 degrees Fahrenheit either indoors or outdoors would have to regularly monitor the temperature and create an injury and illness prevention plan that details how to respond when workers express symptoms of heat illness.

Access to drinking water, a shaded or cool break area, and rest breaks would be required. So would an "acclimatization" plan that ensures new employees can gradually adjust to the heat, such as slowly increasing their workload or giving them 15-minute rest breaks every two hours.

"Notably, acclimatization is the leading killer among the different factors related to heat illness," a senior administration official said. "So 3 out of 4 workers who die on the job due to heat-related heat illness die on that first week and on the job."

At 90 degrees additional requirements kick in, including checking in with workers on the job alone, mandatory paid rest breaks every two hours, and a hazard alert system that reminds employees how to stay safe.

The rule doesn't cover government employees or emergency responders.

Didn't Texas and Florida block heat safety mandates?

Yes, Texas and Florida have blocked local ordinances aimed at protecting workers during extreme heat.

A Florida law that took effect on July 1 bars cities and counties in the state from imposing their own rules on business, like requiring water breaks — something Miami-Dade County considered last year.

Texas Gov. Greg Abbott last year also signed a law that preempts local labor, agriculture, environmental, and other policies that don't align with state codes. Critics said the law overrode the few protections that construction workers in Austin and Houston were guaranteed, including 10-minute breaks every four hours to drink water and rest in the shade. Abbott said the goal was to prevent a patchwork of different rules that would be confusing for businesses.

A senior administration official said OSHA's proposal, if finalized, would apply to all states including Texas and Florida.

Su said she's talked to workers in Texas and Florida, who've asked what a nationwide standard would mean for them. She's reassured them that federal rules would apply in those states, too.

"This rule is meant to make sure that in every state, employers know what the standard is," Su said. "I hear this all the time from employers that having consistency and predictability is very, very important."

Do any states already have heat protection laws?

Yes. Five states have laws that aim to protect employees exposed to heat: Minnesota, California, Washington, Oregon, and Colorado.

A senior administration official said OSHA's proposal is similar to standards that have been successful in those states.

California has had its law on the books since 2006. Washington and Oregon created worker protections after several farm workers died during a heat wave in June 2021.

A senior administration official said OSHA will review state plans to ensure they are at least as effective as the federal rules.

Are businesses opposed to OSHA's rule?

The Guardian reported that some groups representing agriculture and construction companies have lobbied against state and federal efforts to enact heat protection standards. These groups, including the American Farm Bureau Federation and the Construction Industry Safety Coalition, argued that the requirements could be too complex and costly.

But groups that represent farmworkers who pick fruits and vegetables in extreme heat in states like California, Arizona, and Florida have pressured OSHA for years to enact a federal standard.

A senior administration official said OSHA also convened a national advisory committee of construction representatives comprised of management and labor interests.

"That group voted unanimously that we proceed expeditiously with rulemaking," the official said. "So while we may not agree on the contents of the proposal, there are fair number of of employer groups out there that that recognize the importance of a level playing field when it comes to a heat rule."

Are you a business owner or worker who would be affected by heat protection rules? Contact this reporter at cboudreau@businessinsider.com .