Beat the Heat: What Are Ontario’s OHSA Requirements for Working in the Heat?

Quick Hits

• Currently there are no specific heat stress prevention requirements under Ontario’s Occupational Health and Safety Act (OHSA).
• That may change in the future as Bill 222, Heat Stress Act, 2024 received a first reading in November 2024, with a second reading ordered.
• Under the OHSA, employers and supervisors have a general duty to take every precaution reasonable in the circumstances for protection of workers.
• Employers can proactively develop policies and procedures to protect workers in hot environments.

Environment Canada data showed daytime highs nudging 34° C to 35° C (roughly 93° F to 95° F) across Ontario, Quebec, and Nova Scotia from June 22 through June 26, 2025. While heat warnings have subsided for now, forecasters are predicting a warmer-than-average summer.

For employees working outside or in uncooled industrial settings, such as commercial bakeries, foundries, dry-cleaning plants, distribution warehouses, the ambient temperature indoors can climb well past outdoor readings, exposing workers to genuine heat-stress risk.

Currently, Ontario’s Occupational Health and Safety Act (OHSA) and regulations do not feature specific requirements for employers regarding working in heat, such as maximum working temperatures or other safeguards.

However, employers and supervisors, under s. 25(2)(h) and s. 27(2)(c) of the OHSA respectively, have a duty to take every precaution reasonable in the circumstances for the protection of workers.

The government of Ontario’s Guideline No. 33: Working in extreme temperature conditions states that developing hot environment policies and procedures to protect workers in hot environment is a reasonable precaution to take and suggests that employers should implement a heat stress prevention program that establishes:

• worker training in the hazards, health effects, and prevention of heat-related illness;
• criteria or monitoring methods (e.g., acting on heat wave or alert notices by Environment Canada or calculating humidex from temperature and humidity measurements or wet bulb globe temperature measurements);
• a monitoring/sampling plan (e.g., when, where, and what to measure or monitor);
• responses or preventive measures (e.g., increased frequency of breaks, reduced work pace and workload, avoiding working in direct sunlight, scheduling heavy work for cooler part of the day, wearing hats and sun screen outdoors, etc.);
• a water supply plan and encourages hydration (e.g., at least one cup every twenty minutes); and
• first aid and emergency responses, including monitoring of worker symptoms, and investigating incidents of health-related illnesses.

In the United States, several states, such as Arizona, California, and New Mexico, have adopted heat stress standards. These U.S. state laws may provide useful insights in developing a reasonable heat stress prevention program at worksites in the province.

While there is no legislation on working in the heat currently, Bill 222, Heat Stress Act, 2024 completed its first reading on November 7, 2024. The bill has gone to a second reading.

This bill would amend the OHSA by introducing Part IV.1, which would require the minister of labour to develop and implement a worker heat protection standard addressing engineering controls, technology-based measures, and procedural adjustments to protect employees from excessive heat stress. Employers would have to create and periodically review a comprehensive heat stress and protection policy, conduct and share heat stress assessments, and provide workers with necessary protective equipment and cool drinking water. The standard would further mandate training, approved by the chief prevention officer, on heat stress recognition, response protocols, and employees’ rights. Employees would be entitled to their regular rate of pay for any rest periods, breaks, medical removal protection, or training required by the standard. For the first five years after the standard’s implementation, the minister would be required to submit an annual report to the legislature detailing heat stress-related illness and mortality figures and describing enforcement activities.

With temperatures soaring, employers can get ahead of the heat and the legislature by proactively implementing measures to protect workers who are working in extreme heat indoors and outdoors.

Ogletree Deakins’ Canada offices will continue to monitor developments and provide updates on the Cross-Border and Workplace Safety and Health blogs as additional information becomes available.

Follow and Subscribe
LinkedIn | Instagram | Webinars | Podcasts