The Risk of Adopting Nocturnal Work Schedules in Extreme Heat

    [fa icon="calendar"] September 14, 2023 / by Barrow Group Staff

    In response to these climate trends, many employers are switching to nocturnal work schedules.

    Working at Night

    The U.S. Environmental Protection Agency (EPA) characterizes extreme heat as a prolonged period (at least two days) between the months of May and September in which a region’s recorded temperature exceeds the 90th percentile of its historical climate data. Also known as a heat wave, extreme heat can expose individuals to dangerously high temperatures and elevate their risk of experiencing a range of health complications, some of which could prove fatal.

    Extreme heat has become increasingly common across the United States. In fact, the EPA reported that nine of the nation’s 10 hottest years on record have taken place within the past two decades, producing more intense heat waves each year. In response to these climate trends, many employers who leverage outdoor operations have implemented strategies to better protect their workers on the job. One of these strategies is the use of nocturnal work schedules, in which outdoor employees switch from daytime working hours to overnight shifts.

    Nevertheless, nocturnal work schedules carry their own unique safety risks. With this in mind, it’s important for employers to understand these exposures and utilize proper precautions to safeguard their outdoor workers amid extreme heat. This article provides more information on the impact of extreme heat on outdoor employees’ work schedules, outlines the potential risks of implementing nocturnal shifts and offers steps employers can take to keep their workers safe whenever heat waves strike.

    How Extreme Heat Impacts Outdoor Employees’ Work Schedules

    Recent data from the Centers for Disease Control and Prevention (CDC) revealed that extreme heat days currently occur 2.5 times more frequently in the United States than they did in the 1980s. In 2021 alone, the nation recorded a median of 15 extreme heat days across all regions. Even in the country’s coldest areas, the CDC reported that annual heat waves have increased by 40% in the past four decades. Compounding concerns, climate experts project that extreme heat will only continue worsening in the years ahead.

    These conditions have exacerbated occupational safety hazards for outdoor workers, including those in the construction, agriculture, landscaping, mining, waste management and transportation sectors. Namely, these workers are at greater risk of overexerting themselves amid high temperatures and experiencing complications such as dehydration, excess fatigue and, in severe cases, heat-related illnesses (e.g., heat stress, heat exhaustion and heatstroke). According to the latest research from nonprofit organization Public Citizen, extreme heat exposure causes between 600 and 2,000 fatalities and 170,000 injuries each year, making it one of the top hazards in the American workplace.

    In light of these safety concerns, a growing number of employers have implemented nocturnal work schedules for their outdoor employees. Nocturnal shifts are intended to help protect employees from extreme heat hazards by permitting them to work between dusk and dawn, thus reducing their exposure to direct sunlight and daily high temperatures. After all, the warmest time of day generally falls between noon and 6 p.m., peaking around 3 p.m. As such, some of the most common nocturnal shifts are 8 p.m. to 4 a.m. and 11 p.m. to 7 a.m. By working between these hours in cooler temperatures, outdoor employees may be less likely to overexert themselves and experience heat-related ailments, promoting safe and productive operations.

    The Risks of Utilizing Nocturnal Shifts

    Although nocturnal shifts can be beneficial for outdoor employees, they also present the following safety risks:

    • Continued heat exposure—While temperatures typically peak in the early afternoon, they may remain considerably high overnight, especially during heat waves. For instance, if the temperature in a particular location hits 100 degrees Fahrenheit at midday, it could still be as high as 90 degrees Fahrenheit at 8 p.m. Consequently, nocturnal shifts don’t fully eliminate outdoor employees’ exposure to extreme heat. Furthermore, even though temperatures drop between dusk and dawn, humidity levels often rise during this time frame. Humidity could potentially cause outdoor employees who work nocturnal shifts to overheat just as easily as they would during daytime shifts.
    • Increased fatigue—Nocturnal shifts can disrupt outdoor employees’ natural circadian rhythms, making it harder for them to maintain healthy eating, exercise and sleep schedules. This lack of nourishment, activity and rest can cause employees to feel more fatigued and less alert on the job, impacting their overall performance and making them more susceptible to injuries. According to OSHA, occupational incidents and injuries are 18% more likely to occur during evening shifts and 30% more likely to happen during overnight shifts than during daytime shifts. Additionally, fatigue-related productivity concerns cost employers a yearly average of $136.4 billion in lost working time.
    • Diminished overall health—Several studies have shown that working evening and overnight shifts for prolonged periods can elevate employees’ likelihood of experiencing various physical and mental health problems, including insomnia, digestive issues, obesity, high cholesterol, hypertension, diabetes, cardiovascular disease, depression and anxiety. This means that the long-term impacts of nocturnal shifts could end up harming outdoor employees more than helping them.

    Steps Employers Can Take

    Considering the safety exposures associated with nocturnal shifts, it’s best for employers to carefully weigh the pros and cons of these working schedules before utilizing them. If employers do decide to leverage nocturnal shifts for their outdoor employees, they should implement the following risk management strategies:

    • Conduct risk assessments. Prior to commencing nocturnal shifts, employers should perform in-depth risk assessments to identify the specific hazards of evening and overnight work schedules. They should also ensure they have the resources needed to keep outdoor employees safe, such as high-visibility personal protective equipment (PPE).
    • Provide education. Employers should provide outdoor employees with proper training on upholding healthy eating, exercise and sleeping patterns while working nocturnal shifts. Specifically, workers should be encouraged to get between seven and nine hours of sleep each day, maintain a balanced diet, engage in daily physical activity, take naps before each shift, and avoid consuming fatty foods or excessive amounts of caffeine on the job.
    • Make necessary changes to the job site. Adjusting certain aspects of the work environment (e.g., providing additional lighting and offering extra breaks) can help outdoor employees stay alert and prevent injuries during nocturnal shifts.
    • Monitor employees. Employers should routinely assess outdoor workers for signs of fatigue (e.g., low energy, slowed reflexes, poor decision-making and irritability) and adjust their schedules and workloads as needed to help them stay healthy and avoid incidents on the job.

    Regardless of whether employers utilize daytime or nocturnal shifts for their outdoor workers, they should consider these best practices to protect employees from extreme heat:

    • Encourage proper precautions. It’s crucial for employers to inform employees of valuable precautions to take when working during heat waves. This includes applying (and frequently reapplying) sunscreen during the day, drinking plenty of water, eating healthy snacks, selecting lightweight and breathable clothing, wearing a brimmed hat and sunglasses (if necessary), and utilizing required PPE.
    • Allow workers to hydrate and recover. Employees should receive periodic water breaks in shaded or air-conditioned areas to mitigate the risk of dehydration and allow them time to recover from any physically demanding tasks during their shifts.
    • Promote adequate response measures. It’s vital to teach employees the key signs of heat-related illnesses (e.g., excessive sweating, high body temperature, nausea, headache, dizziness and confusion) and instruct them to consult their supervisors if they experience any of these symptoms, seeking medical attention when necessary.
    • Ensure compliance. Employers should consult legal counsel to confirm that their strategies for protecting outdoor workers from extreme heat comply with all applicable federal, state and local safety regulations. This legislation may include OSHA’s general duty clause, the National Institute for Occupational Safety and Health’s recommended heat standard, and certain OSHA-approved state plans (e.g., California, Minnesota and Washington) regarding heat exposure.


    Extreme heat can present serious hazards for outdoor workers. While nocturnal shifts can help alleviate some of these concerns, they may also lead to additional safety exposures. By better understanding the risks of nocturnal work schedules and appropriate mitigation strategies, employers can help keep their outdoor employees happy and healthy in the heat.

    Contact us today for more risk management solutions.

    Topics: risk management, Environmental Protection Agency, Climate Change, OverNight Shifts, Outdoor Workers, Extreme Heat, Nocturnal Work Schedule

    Barrow Group Staff

    Written by Barrow Group Staff

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