Working outdoors during heat events

Working outdoors during a heat event can expose employees to heat stress and heat-related illness. People leaders are responsible for assessing risks, putting appropriate safety measures in place and monitoring conditions and employees.

Use this page to assess worksite conditions and find guidance, tools and training for working safely during heat events. For the purposes of this page, people leaders include supervisors and managers responsible for employees performing outdoor work.

On this page

• Heat events and heat stress
• Assess heat risks for outdoor work
• Responsibilities of people leaders
• Assess conditions at the worksite
  • Use the Heat Stress app
• Train employees about heat stress
• Exposure control plans and support
• Related resources

Heat events and heat stress

Heat events, or heatwaves, involve high temperatures and sometimes high humidity. These events are usually hotter than the seasonally normal temperatures for your region.

B.C. is experiencing an increase in average summer temperatures and extremely hot days. As the climate changes, we can expect heat events to be hotter, more frequent and longer lasting.

Heat events can affect anyone’s health. Unusually high heat can have serious and negative impacts on your health, and some people are at greater risk, including older people, pregnant people and people with chronic health conditions.

Wildfires can coincide with heat events and create conditions for exposure to wildfire smoke and extreme heat together.

What is heat stress?

Heat stress occurs when a person is exposed to conditions that result in a core body temperature exceeding 38°C or 100°F (normal is 37°C or 98.6°F). Depending on the work environment, the body adapts and maintains its normal temperature by sweating and increasing skin blood flow to prevent body temperature from rising.

Heat stress and heat-related illnesses occur when the body overheats from prolonged exposure to high temperatures.

If core body temperature rises and steps are not taken to reduce body temperature, effects may include heat cramps, heat exhaustion and heat stroke. Medical intervention is likely required.

People leaders and employees must take steps to avoid hazardous exposure to heat while working outside.

Assess heat risks for outdoor work

WorkSafeBC considers no single temperature to be unsafe for work. Several components are assessed when determining heat safety for employees:

• Temperature
• Humidity
• Direct sunshine or shade
• Level of physical exertion
• Clothing
• Duration of the exposure to extreme high temperatures
• The ability of the worker(s) to acclimatize to the environment

People leaders are responsible for ensuring the safety of their employees when they are working in hot conditions that may cause heat stress.

During a heat warning

If there is a heat warning issued by public health authorities for the area that employees are working outside, evaluate if the work can be rescheduled (based on your weather forecast, including early in the day). If the work must be completed, make sure a plan is in place to evaluate site conditions and mitigate the heat risk to employees.

During an extreme heat emergency

If an extreme heat emergency is declared, only critical outdoor work should proceed with a full exposure control plan. Employee health and medical monitoring may also be required. All non-critical outdoor work should be rescheduled.

For assistance with a heat exposure control plan, contact a BC Public Service Agency occupational safety specialist for advice by submitting a service request via AskMyHR. Choose service category Workplace Safety and sub-category Other Issues and Inquiries.

Responsibilities of people leaders

People leaders supervising outdoor work must assess heat risks and take appropriate measures to protect employees. People leaders must:

• Assess the risk of heat stress or illness to employees when the temperature outside is more than 23°C
• Train employees about the risks of heat exposure. This can be done prior to starting the season for outside work and at regular safety, toolbox or tailgate meetings
• Implement the risk mitigations as required
• Inform employees working outside that the mitigation strategies being used are based on the daily and current heat conditions
• Make sure the worksite is monitored for increased temperatures and reassess the risk throughout the shift as necessary
• Monitor employee health and safety

Assess conditions at the worksite

Download the IATSE 891 Heat Stress app

The IATSE 891 Heat Stress app can be downloaded by searching ‘IATSE 891’ in any app store or via these direct links to Google Play and the Apple store.

Use the IATSE 891 Heat Stress app

To use the app, you must know the temperature and humidity of the work location and answer a few questions about the work.

While Environment Canada or a nearby weather station (use the closest) may be used, these should be used with caution because temperature and humidity can vary the farther the worksite is from the weather station. Assess conditions at the actual work location whenever possible, particularly when a worksite is exposed to direct sunlight or has limited air movement.

For worksites in place for multiple days or sites that are not close to a weather station, the worksite must have a thermometer and hygrometer (measures humidity) to complete regular assessments. During a declared extreme heat emergency, worksite temperature and humidity measurements must be taken and entered into the IATSE 891 Heat Stress app.

Complete an assessment

Conduct assessments throughout the day including during the warmest portion of the day.

1. Obtain the temperature and humidity for the worksite
2. Enter information about the work being performed
3. The app creates an instant report on heat stress risk. Review the identified risks
4. Implement the mitigation protocols indicated in the app's What to Do? section of the report
5. Take a screenshot of the app’s final report each time an assessment is completed
6. Keep it for your records and to track environmental changes to the worksite
7. Reassess conditions throughout the day and wherever conditions or work activities change
8. If the Humidex or regular temperature is over 30°C, you must reassess hourly and implement new mitigation strategies as needed

Train employees about heat stress

• What heat stress is and how it develops
• Personal factors that affect heat stress
• How to recognize symptoms of heat stress
• What workers should do if they or their coworkers develop a heat-related illness

Recommended resources for employee training

People leaders can use the following resources to support employee training:

• 7-minute training video (YouTube)
• Toolbox talk: Working in hot weather (ActSafe Safety Association)
• Heat Stress (WorkSafeBC)
• Hot temperature: Heat stress (BC Municipal Safety Association) (DOC, 670KB)
• Working in the heat (Canadian Centre for Occupational Health and Safety)
• Heat-related illness: Watch for signs (Canadian Centre for Occupational Health and Safety)
• Health checks during extreme heat events (National Collaborating Centre for Environmental Health)
• Extreme heat (Interior Health)

Exposure control plans and support

While this information focuses on working outside, ministries may have other workplace settings that create a risk of heat stress for workers. For assistance identifying job tasks or positions and conducting a heat stress assessment, contact a BC Public Service Agency occupational safety specialist for advice by submitting a service request via AskMyHR. Choose service category Workplace Safety and sub-category Other Issues and Inquiries.