Cold work warm-up schedule: how long can you work in the cold?
Enter air temperature and wind speed, and the tool returns the ACGIH maximum work period and number of 10-minute warm-up breaks for a 4-hour shift of moderate to heavy work. Extra breaks start at -26°C (-15°F) with a 16 km/h (10 mph) wind; at -43°C (-45°F) and below, non-emergency work should cease in any wind.
Cold work warm-up schedule
Based on the ACGIH work/warm-up schedule for a 4-hour shift (air temperature under a sunny sky), as reproduced by WorkSafe Saskatchewan. For workers in dry clothing.
How to read it: work for no longer than the maximum work period, then take a 10-minute warm-up break in a warm place; the number of breaks is per 4-hour period, with an extended break (such as lunch) in a warm place at the end. Light work uses the schedule one step colder, as ACGIH directs. Our design choices, not part of the ACGIH table: a temperature between two bands uses the colder band, and wind between two columns uses the windier column. This tool supports, and does not replace, your employer's cold stress program or local regulations.
How do you use the warm-up schedule tool?
The tool reads the ACGIH Threshold Limit Value (TLV) work and warm-up schedule, as reproduced by WorkSafe Saskatchewan and in a 2022 cold stress standard used at the US Department of Energy's Hanford Site. It gives one answer per 4-hour block: the longest continuous work period and how many warm-up breaks to schedule.
For the reasoning behind the schedule, its history and how to adapt it on real sites, read our explainer on work and warm-up schedules. This page is the lookup and the arithmetic.
Step 1: enter air temperature (dry bulb, not wind chill) in °C or °F.
Step 2: enter sustained wind speed, or pick a visual cue: a light flag moving is about 8 km/h (5 mph); a fully extended flag, 16 km/h (10 mph); a newspaper sheet lifting, 24 km/h (15 mph); blowing and drifting snow, 32 km/h (20 mph).
Step 3: choose moderate to heavy work, or light work, which shifts the answer one step colder.
Step 4: read the maximum work period, the number of breaks and whether non-emergency work should cease.
What does the full ACGIH schedule say?
Each cell shows the maximum work period in minutes and the number of breaks in the 4-hour period. Temperatures are air temperatures under a sunny sky. "Stop" means non-emergency work should cease. The 120-minute, 1-break cells are normal breaks.
| Air temp °C (°F) | No noticeable wind | 8 km/h (5 mph) | 16 km/h (10 mph) | 24 km/h (15 mph) | 32 km/h (20 mph) |
|---|---|---|---|---|---|
| -26 to -28 (-15 to -19) | 120 min, 1 | 120 min, 1 | 75 min, 2 | 55 min, 3 | 40 min, 4 |
| -29 to -31 (-20 to -24) | 120 min, 1 | 75 min, 2 | 55 min, 3 | 40 min, 4 | 30 min, 5 |
| -32 to -34 (-25 to -29) | 75 min, 2 | 55 min, 3 | 40 min, 4 | 30 min, 5 | Stop |
| -35 to -37 (-30 to -34) | 55 min, 3 | 40 min, 4 | 30 min, 5 | Stop | Stop |
| -38 to -39 (-35 to -39) | 40 min, 4 | 30 min, 5 | Stop | Stop | Stop |
| -40 to -42 (-40 to -44) | 30 min, 5 | Stop | Stop | Stop | Stop |
| -43 and below (-45 and below) | Stop | Stop | Stop | Stop | Stop |
What rules come with the table?
The numbers only hold under the assumptions printed with them. WorkSafe Saskatchewan and the Hanford reproduction agree on four points.
The schedule applies to any 4-hour period of moderate to heavy work, with an extended break, such as lunch, in a warm location at the end.
A warm-up break means 10 minutes in a warm location.
The TLVs apply only to workers in dry clothing.
For light-to-moderate work with limited physical movement, apply the schedule one step lower (one row colder).
How does the light-work adjustment change the answer?
People who stand, watch or operate equipment make less body heat, so the table moves them one row colder in the same wind column. The ACGIH example: at -35°C (-30°F) with no noticeable wind, heavy work allows 55 minutes with 3 breaks, while a job with little physical movement gets 40 minutes with 4 breaks.
If the step down lands on a Stop cell, the tool returns Stop. At -40 to -42°C (-40 to -44°F) in calm air, for example, heavy work allows 30 minutes with 5 breaks, but light work falls into the -43°C row, where non-emergency work should cease.
| Conditions | Work type | Max work period | Breaks per 4 hours |
|---|---|---|---|
| -27°C (-17°F), 16 km/h (10 mph) | Moderate to heavy | 75 min | 2 |
| -30°C (-22°F), 24 km/h (15 mph) | Moderate to heavy | 40 min | 4 |
| -30°C (-22°F), 24 km/h (15 mph) | Light | 30 min | 5 |
| -36°C (-33°F), no noticeable wind | Moderate to heavy | 55 min | 3 |
| -36°C (-33°F), no noticeable wind | Light | 40 min | 4 |
| -38°C (-36°F), 16 km/h (10 mph) | Any | Stop | None |
How do you turn the result into a shift plan?
Divide the 4-hour block into work periods no longer than the maximum, separated by 10-minute warm-up breaks, and end the block with the extended warm break. At 40 minutes with 4 breaks, the breaks alone add 40 minutes of warm-up time, which crews need to plan for in staffing and task sequencing.
The tool rounds conservatively: when a reading falls between published bands or wind columns, it uses the colder band and the next higher wind column. That is a design choice for safety, not part of the ACGIH table.
If only a wind chill cooling rate is available, the Government of Ontario's film and television safety guidelines, which reproduce the Saskatchewan schedule, start special warm-up breaks at about 1750 W/m² (equivalent temperature -32°C) and stop non-emergency work at or before 2250 W/m² (-51°C).
When does the schedule not apply?
Above -26°C (-15°F), the table adds no breaks beyond normal ones, but that does not mean there is no cold stress. CCOHS reports that the ACGIH suggests a work-warming regimen for continuous work at a wind chill of -7°C (19.4°F) or below, and added measures such as constant observation and adjusted work pace at -12°C (10.4°F).
The table also assumes dry clothing. Wet gloves, socks or base layers, rain, sleet, water work and sweat-soaked layers all fall outside it, so employers should add breaks and dry changes. Anyone with numbness that does not resolve, uncontrolled shivering or confusion should stop work and be checked, and ongoing symptoms warrant a visit to a clinician.
Key takeaways
The ACGIH schedule covers a 4-hour block of moderate to heavy work in dry clothing, with 10-minute warm-up breaks.
Extra breaks start at -26°C (-15°F) with a 16 km/h (10 mph) wind.
At -43°C (-45°F) and below, non-emergency work should cease in any wind.
Light work moves the answer one row colder.
Earlier ACGIH triggers apply at a wind chill of -7°C and at -12°C, even though the table starts at -26°C.
Frequently asked questions
How long can you work outside at -30°C?
At -29 to -31°C (-20 to -24°F) with no noticeable wind, moderate to heavy work follows normal breaks: 120 minutes with 1 break per 4 hours. With a 24 km/h (15 mph) wind, the maximum drops to 40 minutes with 4 breaks.
At what temperature should outdoor work stop?
Under the ACGIH schedule, non-emergency work should cease at -43°C (-45°F) and below in any wind. It stops at milder temperatures when wind rises, for example at -32 to -34°C (-25 to -29°F) with a 32 km/h (20 mph) wind.
How long is a warm-up break?
The schedule assumes each warm-up break is 10 minutes in a warm location. It also assumes an extended break, such as lunch, in a warm place at the end of each 4-hour period.
Should I enter wind chill or air temperature?
Enter air temperature and wind speed separately. The ACGIH table already combines the two, so entering a wind chill value would count the wind twice.
Is the ACGIH warm-up schedule a legal requirement?
It is a guideline published by ACGIH, and whether it is enforceable depends on your jurisdiction. Check your provincial, state or federal occupational health and safety rules, and write the schedule into your site cold stress plan.
Related reading
Sources
Working in Cold Conditions (fact sheet with work warm-up schedule), WorkSafe Saskatchewan
Cold Stress, TFC-ESHQ-IH-STD-01 (Attachment A: TLVs Work/Warm-Up Schedule for Outside Workers Based on a Four-Hour Shift), Hanford Site, US Department of Energy
Cold Environments: Control Measures, Canadian Centre for Occupational Health and Safety
Safety guidelines for the film and television industry: Appendix C, adverse weather conditions, Government of Ontario
About HEATJAC. HEATJAC is a thermal architecture company founded by an anesthesiologist. We design patented garment systems that capture, conduct and broaden warmth across the body, and we publish this knowledge hub because the science of staying warm should be public. HEATJAC products are not medical devices and are not intended to diagnose, treat, cure or prevent any disease.