Be Heat Smart! Your Outdoor Heat Safety Program

Working outdoors in the heat can become hazardous days, or even weeks, before May 1, when Washington State’s Outdoor Heat Exposure rule kicks in.

To ensure better preparedness, employers are encouraged to start heat safety planning, training, and other preparations in early spring, or sooner.

A workforce that is unprepared for outdoor heat is at increased risk for heat exhaustion and life-threatening heat stroke. Even the healthiest worker can get sick when working outdoors in the heat without proper protections. Also, heat illness can make workers more susceptible to falls, equipment-related injuries, and other on-the-job safety hazards.

The rules and resources on this page can help employers plan, prepare, and train for heat illness prevention. Some resources proactively address topics not covered in the current rule, such as shade, rest breaks, and acclimatization.


Current Outdoor Heat Exposure rules include requirements to:

  • Address outdoor heat exposure safety as part of your required Accident Prevention Program.
  • Provide annual training to employees and supervisors on symptoms of outdoor heat exposure and policies in place to prevent heat-related illness.
  • Provide a sufficient amount of drinking water to employees and an opportunity to drink it on days when temperatures require preventive measures.
  • Respond appropriately to any employee with symptoms of heat-related illness.

In addition to current requirements, L&I recommends employers choose to:

  • Provide adequate shade (or alternative cooling methods) at all times, to allow for access to prevent or respond to heat illness.
  • Encourage and allow workers to take paid, preventative cool down rest periods so they don’t overheat; and, when temperatures are 90°F or hotter, require workers to take additional paid, cool down rest periods of at least 10 minutes every 2 hours. Longer and more frequent breaks are indicated if temperatures continue to rise to 100°F.
  • Make sure supervisors and employees always have a way to communicate with each other so they can promptly report heat illness and get medical assistance, if needed.

Current Outdoor Heat Exposure Rules

L&I is conducting rulemaking on Ambient Heat Exposure

Training & Resources

Accident Prevention Program (APP)

Use of these templates is optional. They address current rule requirements and include additional prevention measures such as shade, rest breaks, and acclimatization.

Please customize the content so it reflects the working conditions and safety precautions at your job sites:

Training Resources and Other Information

When using any of the follow training resources, be sure to discuss the specific conditions and safety precautions to follow for each worksite.

Training Courses

  • Heat Illness training kit (updated 6/15/2022) helps covers the basics for an instructor-led presentation. It also includes additional prevention information about shade, rest breaks, and acclimatization.

Additional Training and Information Resources

Search Safety & Health topics for "Outdoor Heat" to find more resources.

Questions & Answers

These Questions and Answers are based on the current Outdoor Heat Exposure (OHE) rules.

Rule Coverage

Q: When does the outdoor heat exposure rule go into effect?

The rule is in effect May 1st through September 30 of every year.

Q: What about other times of the year?

It is possible to have outdoor heat hazards before May 1st and after September 30, so employers who start earlier to plan, train, and equip crews will be better prepared to keep their workforce productive and healthy.

Q: Who must follow the rule?

Any employer with employees who work outdoors.

Q: What if an employee works outdoors for only a short time?

Employees who work outdoors for less than 15 minutes in a 60-minute period are considered to have incidental exposure and are not covered by the rule.

Q: What about employees who drive for their job?

It depends; employees who drive motor vehicles are not considered “working outdoors” only when the employee can stay cool inside due to air conditioning or airflow created by fans, vents, or open windows. The same goes for employees operating machinery from inside a cab.

Q: Are truck drivers covered by the rule when performing loading, unloading, or other activities outside their rig?

No, if they have only incidental exposure (i.e., less than 15 minutes exposure in a 60 minute period).

Q: Is working inside a temporary containment structure connected to the side of a building or similar structures considered an outdoor environment?

Work environments such as inside vehicle cabs, sheds, and tents or other structures may be considered an outdoor environment if the environmental factors affecting temperature are not managed by engineering controls

Temperature Action Levels and Clothing

Q: Who determines the outdoor temperature?

Employers are responsible for tracking the temperature at the actual work site throughout the workday.

Employers may not rely only on the weather stations since that information may not reflect the temperatures at the actual worksite. Employers can use a simple thermometer to take temperature readings at the worksite. Temperature records are not required.

Q: What about using the Heat Index?

Employers do not need to measure humidity or the Heat Index. They only need to know the work site ambient temperature and type of clothing worn by workers.

Q: What if an action level temperature doesn’t happen until late afternoon?

Outdoor heat safety requirements won’t apply until one of the temperature action levels in Table 1 is met.

Employers could schedule work during earlier, cooler morning times to help prevent the risk for heat illness.

Q: How do you distinguish between double-layer and vapor barrier clothing?

Vapor barrier clothing does not let sweat evaporate from the body or air to reach the skin. Double-layer clothing allows for some evaporation of sweat and for air to reach the skin.

Q: What about a sweatshirt (hoodie) or flannel shirt worn over a T-shirt?

A t-shirt worn as an undergarment with a sweatshirt or shirt would fall under the 89°F category.

Q: What Table 1 category does Tyvek™ fit under?

It depends on the Tyvek™ worn. For example, Tyvek™ 400 Series would fall under the 77°F category since it lets sweat evaporate and air to reach the skin.

Q: How about rain wear?

Rainwear that lets sweat evaporate and air to reach the skin, such as Gore-Tex or eVent, would fall under the 77°F category.


Q: Do employers only need to provide drinking water from May through September?

Employers must provide drinking water no matter what month it is

In addition to the Outdoor Heat Exposure rules, other rules with potable drinking water requirements apply, such as WAC 296-155-140 for construction and WAC 296-800-23005 for general industry.

Q: What does a “sufficient” amount of water mean?

This means water is always available to all employees.

The employer is responsible for providing enough water for each employee to drink at least one quart per hour.

Q: Do I have to provide bottles of water?

No. Bottled water is just one option, employers can also provide potable drinking water in other ways

Q: Can we use an outside faucet and garden hose to fill containers?

An outside faucet (hose bib) providing potable water may be used to fill containers, but, for sanitary reasons, it’s not acceptable for employees to drink directly from a faucet.

Water running through a garden hose can become contaminated due to leeching so it’s not acceptable to use a garden hose for filling containers or to drink directly from one -- unless the manufacturer states that the hose and connectors are approved for potable drinking water systems.

Q: Are individual drinking cups required?

Yes. Sharing cups is unsanitary are not allowed.

Q: What if employees bring their own water?

Employers must still ensure an adequate supply of water is available and each employee has the opportunity to drink at least a quart of water an hour.

Q: Are sports drink okay?

Electrolyte-replenishing beverages (sports drinks) that don’t have caffeine are acceptable.

Q: What temperature should the water be?

The rule requires water to be suitable to drink. Water so hot that a worker won’t want to drink it, would not be considered suitable.

Although there is no specific temperature mentioned for drinking water in the outdoor heat exposure rule, 50–60 degrees is generally acceptable.

Q: How can we keep water within a suitable temperature range?

Employers should consider what could work best for each job site. Some ideas include storing water under shade, providing insulated coolers or dispensers with ice, and other safe and sanitary options.

Q: Can water be kept in a common place such as an air-conditioned work trailer?

Yes, as long as it is readily accessible and remains suitable to drink.

Q: Can an employee walk to a neighboring building to get water?

Yes, as long as the building is within a reasonable distance and the water is readily accessible.

Q: What about employees who can’t leave their work area (e.g., paving crew, flaggers, lead containment areas, etc.)?

Employers must make sure water is readily accessible where employees are working

Q: How would you expect employees that must travel from location to location to get water?

Employees must be able to stop to obtain water or carry sufficient quantities with them.

Q: What can an employer do if an employee refuses to drink water?

Employers must provide water, ensure it’s accessible, encourage drinking, and emphasize the importance of hydration during safety training. They cannot force an employee to drink the water.

Response to Heat Illness

Q: What must an employer do to respond to heat illness?

Employers need to have a plan and trained employees to respond appropriately when someone shows or reports signs or symptoms of heat illness.

The employer must ensure the worker is relieved from duty, provided with shade or other sufficient means to cool down, and tracked to determine whether medical attention is necessary.

Early detection of heat illness and a prompt response lowers the risk for a medical emergency or even death.

Q: Are employers required to provide shade?

Shade, or another sufficient means for cooling down, must be available at all times for an employee showing signs or symptoms of heat illness.

Plan and Train

Q: What are the training requirements and procedures the outdoor heat exposure?

All employers must have a written Accident Prevention Program (APP) that addresses outdoor heat exposure planning and safety training.

Workers and supervisors must be trained before working in the heat and yearly after that.

Q: Can an employer print off the heat stress information off the L&I website and show it at a safety meeting? Is that proper training?

Yes, as long as the training covers the required information specified in the rule, including employer and site-specific information.

Need help with your Outdoor Heat Exposure Program or Accident Prevention Program? 

Contact an L&I Safety & Health consultant near you. We offer no-charge services and can answer questions you may have.