3 states have real heat rules for outdoor workers, Colorado only counts the injuries

Which states have heat rules for outdoor workers is a narrower list than it looks

Which states have heat rules for outdoor workers is a narrower list than it looks. California, Washington and Maryland each require an employer to act once the temperature passes a set number, with a real requirement behind it today. Colorado passed a heat law in 2026 that sounds like a fourth, and reading its actual bill text directly, rather than trusting how the law was described when it passed, shows that it is not one. The federal government proposed its own nationwide heat standard in August 2024, and more than 2 years later it still has not become final.

What California, Washington and Maryland actually require

California heat illness prevention rule has required shade once the temperature passes 80 degrees Fahrenheit since it first took effect on August 22, 2005, now about 21 years in force, a span this site counts from that date to today. At 95 degrees Fahrenheit, agricultural workers get a mandatory 10 minute cool down rest every 2 hours, and every outdoor employer must give workers 1 quart of water an hour. Washington outdoor heat rule, in force since July 5, 2008, sets 2 triggers depending on clothing, 80 degrees Fahrenheit in ordinary clothing and 52 degrees Fahrenheit for workers in nonbreathable or vapor barrier clothing, gear that traps heat against the body, and requires shade, cool water, a rest on request and a written accident prevention plan. Maryland heat stress standard, the newest of the 3, took effect September 30, 2024, covering indoor and outdoor work alike at a heat index of 80 degrees Fahrenheit, a single number combining air temperature and humidity, when a written prevention plan becomes mandatory, rising to a 90 degree high heat trigger that adds a mandatory rest, 10 minutes every 2 hours up to 100 degrees and 15 minutes every hour above it, plus 32 ounces of water an hour.

Colorado counts the injuries, it does not yet set a number

Colorado signed its own heat and cold law, H.B. 26-1272, on June 4, 2026, and it took effect August 12, 2026. Reading the bill text directly, rather than the framing that circulated when it passed, shows it orders 1 state agency to start counting worksite heat and cold injuries by January 15, 2027 and to publish a voluntary model plan by July 1, 2028, funded by a 76,651 dollar appropriation. It sets no temperature trigger, no rest break and no written plan requirement for any employer today. That correction, found only by reading the enacted text itself, is why Colorado does not belong on the same list as California, Washington and Maryland.

The federal rule proposed in 2024 still has not become final

The Occupational Safety and Health Administration, the federal agency that regulates workplace safety, proposed a nationwide heat standard on August 30, 2024, in the Federal Register, the government record where new rules are proposed, at citation 89 Fed. Reg. 70698. By April 29, 2026, about 20 months later, Senate Bill S.4427 was introduced to block that same proposal from ever becoming final. Maryland own standard took effect just 1 month after the federal proposal existed, a comparison this site draws directly from the 2 dates each source states. Until a federal rule is finalized or blocked, the outcome for most outdoor workers in the country still depends entirely on which state they work in.