Learn more about Maryland OSHA’s heat rules – including indoor and outdoor standards, as well as shared employer requirements.
Maryland’s OSHA Heat Stress Standards govern employers whose employees’ workplace, whether indoor or outdoor, has a heat index which exceeds 80 degrees Fahrenheit. They must monitor heat index, provide shade, and cool drinking water. The chart below summarizes Maryland OSHA heat regulations, set forth by COMAR 09.12.32.
| Employers may also follow current NIOSH work/rest recommendations or demonstrate effective protection through documented alternative cooling measures. |
Implement high-heat procedures, including a work/rest schedule adjusted for conditions, workload, clothing, and PPE. Monitor employees for heat illness.
Provide at least 10 minutes of rest every two hours worked.
Provide at least 15 minutes of rest every hour worked.
Maryland’s first heat regulation took effect in 2020, and full indoor and outdoor heat protections were established in 2024.
Maryland OSHA heat regulations apply to indoor and outdoor workplaces at a heat index of 80°F or higher. Covered employers must provide water, shade or alternative cooling, acclimatization, training, emergency procedures, and a written heat illness prevention plan.
Track on-site WBGT and heat index so your EHS team can make better informed, more accurate decisions.
Track real-time WBGT and heat index where your crews work.
See changing heat conditions across your jobsites in one dashboard.
Use on-site readings and predictive forecasts to guide decisions about breaks, cooling, and work schedules.
Keep your crew safe and productive with automated work/rest guidance based on real-time WBGT.
Automate work/rest guidance as on-site WBGT changes.
Account for workload, PPE, and worker acclimatization.
Give supervisors clear direction on when crews should work and rest.
Send supervisors and workers automated alerts with instructions based on your site’s heat safety policy.
Notify supervisors and workers when conditions exceed your policy’s heat thresholds.
Include clear instructions for rest breaks, hydration, and cooling.
Customize alert groups so the right people receive the right guidance.
Use on-site hardware to record on-site weather conditions and export historical data to support inspections, incident reviews, and program evaluation.
Automatically log on-site weather conditions throughout the workday.
Export historical data to support inspections and incident reviews.
Review past heat exposure to evaluate and improve your heat safety program.
OSHA’s proposed federal heat standard has not yet become a final rule. Construction employers already have a duty to protect workers from recognized serious heat hazards under OSHA’s General Duty Clause. Existing requirements for drinking water, first aid, and injury reporting also apply. Employers must follow any applicable state heat illness prevention rules.
OSHA’s proposed heat standard would require covered construction employers to develop a heat illness prevention plan, monitor heat conditions, and provide training and emergency procedures. The proposal includes protections beginning at a heat index of 80°F and additional measures at 90°F, including 15-minute rest breaks at least every two hours. It also allows WBGT-based triggers.
OSHA’s heat National Emphasis Program, or NEP, directs inspections and outreach toward workplaces with elevated risks of indoor and outdoor heat exposure, including construction. Updated in April 2026, the program helps OSHA identify heat hazards and evaluate employers’ prevention measures. The NEP is an enforcement program; it does not establish a separate heat standard or replace applicable state requirements.
There is no single nationwide OSHA temperature cutoff for construction work. Heat risk depends on humidity, direct sunlight, workload, PPE, and whether workers are acclimatized. Dangerous conditions can develop below heat advisory thresholds. Employers should assess individual jobsite conditions and apply the monitoring, cooling, rest, and work modification requirements that govern their state and operations.
WBGT generally provides a more complete assessment of jobsite heat exposure because it accounts for humidity, radiant heat, air temperature, and air movement. Heat index combines temperature and humidity and can underestimate exposure in direct sunlight. OSHA recommends WBGT for a more accurate assessment, alongside workload and clothing adjustments. Employers should use the measurement method required by applicable state heat rules.
Federal OSHA does not currently have one universal heat-related work/rest schedule for construction workers. OSHA recommends increasing the frequency and duration of breaks as heat stress rises, considering WBGT, workload, protective clothing, and acclimatization. Workers should recover in a cooler area. Applicable state heat rules may establish mandatory break schedules or other specific requirements.
Heat acclimatization is the gradual process of building tolerance to working in hot conditions. New workers and workers returning after time away may need reduced heat exposure, closer supervision, and more frequent breaks. OSHA recommends gradually increasing exposure over the first one to two weeks. Acclimatization procedures should also follow any applicable state requirements.
A construction heat illness prevention plan should explain how the employer monitors heat, provides drinking water and cooling areas, schedules rest breaks, and acclimatizes workers. It should also assign responsibilities, describe worker and supervisor training, and establish emergency response procedures. Tailor the written plan to each jobsite’s conditions, work activities, and applicable heat illness prevention requirements.
OSHA recommends monitoring weather conditions before and during outdoor work. Darkening clouds, increasing winds, thunder, and lightning can all signal and approaching storm.
Stop work and seek shelter immediately when thunder is heard.
Move workers to a safe shelter, or if unavailable, a hard-topped metal vehicle with windows closed.
Wait at least 30 minutes after the last clap of thunder before returning outdoors. If thunder is heard again, the timer is reset.
OSHA recommends a written lightning safety procedure as part of an emergency action plan – so workers know when to stop work, where to shelter, and when operations can resume.
Monitor forecasts and changing conditions. Consider rescheduling outdoor jobs or pours when thunderstorms are expected.
Establish a clear warning process when lightning occurs. Show how workers will receive lightning warnings and instructions.
Identify shelters and evacuation zones, allowing enough time for every worker to reach safe shelter.
Strobe lights, loud alarms, and text-to-speech alert your crew when lightning strikes nearby.
Broadcast clear instructions with custom text-to-speech messages so workers know where to go and what to do.
Keep alerts running with a solar-powered, cellular system that operates independently of site power and Wi-fi.
Know when lightning is coming, and when work might have to stop with immediate notifications and SMS.
Keep crews informed with automatica all-clear notifications when your policy’s waiting period ends.
Customize alert groups and messages by crew, location, and role across large jobsites.
Plan time-sensitive work around a shared, in-app lightning countdown.
See how much time remains before your policy’s required waiting period ends.
Automatically reset the timer with each new strike inside your policy’s radius, so supervisors have a consistent all-clear for restarting work.
OSHA does not have a standalone lightning safety standard covering all construction work. However, employers must protect workers from recognized serious hazards, including lightning, under the General Duty Clause. OSHA and NOAA publish recommendations to help employers plan for thunderstorms and protect outdoor crews.
OSHA recommends taking action when workers hear thunder, see lightning, or notice signs of an approaching thunderstorm. If thunder is heard, workers should immediately move to safe shelter. Employers should plan evacuation early enough for everyone to reach safety before the storm arrives.
OSHA’s general lightning safety guidance does not establish a universal shutdown radius, such as 8 or 10 miles. Employers should establish procedures for suspending work that account for jobsite conditions and the time crews need to reach shelter. Hearing thunder is a signal to seek shelter immediately.
OSHA recommends remaining in safe shelter for at least 30 minutes after the last sound of thunder. Every additional rumble restarts the waiting period. Rain stopping or skies clearing does not replace that recommended waiting period.
A fully enclosed building with electrical wiring and plumbing is the preferred shelter. If one is unavailable, OSHA recommend sa hard-topped metal vehicle with its windows closed. Tents, open-sided shelters, and covered porches do not provide adequate lightning protection. Identify suitable shelters before outdoor work begins.
A lightning safety plan should explain how crews receive warnings, where they shelter, and how much time they need to get there. It should also define when outdoor work stops and resumes. OSHA recommends including these procedures in a written emergency action plan and training workers to follow them.
Yes. Workers can be exposed to lightning outside the area of rainfall. A dry jobsite does not mean a thunderstorm is a safe distance away. Crews should monitor approaching weather and seek shelter immediately when thunder is heard, even if rain has not started.
Watch how construction sites across the country use Perry Weather to comply with OSHA guidelines and keep their workers safe.
