The three measures are the mean, the median, and the mode, each computed from your count-day heat index readings. Compare all three against Oregon's 80 and 90 degree Fahrenheit thresholds to decide your count-day duties.
- mean: add all readings, divide by the count
- median: the middle value when readings are lined up low to high
- mode: the reading that appears most often; a repeat value may just be a rounding effect, so treat the mode as a supporting figure
- At 80 degrees Fahrenheit or above, drinking water must be immediately and readily available at all times, at no cost, enough for up to 32 ounces per hour
- At 90 degrees Fahrenheit, when controls cannot bring exposure below that level, high-heat practices apply, including a written rest break schedule
1. Gather every heat index reading for the count area before you start counting
You take heat index readings in the count area because the readings decide what your crew does on a hot day. The heat index combines air temperature and humidity into one number. It is the number that drives the rules. So collect the readings first, while the area is quiet and before the count starts and bodies add heat.
Log each reading with a time and a spot. A large stockroom has warm zones near a roof line, cool zones by a door, and spots in between. Several readings across the shift will show you the pattern. One reading at a random moment shows you very little.
Keep the raw readings in a list. You will need the full set for step three, where you summarize the readings. Store the readings in your existing count file or a simple sheet. Do not clean the list by deleting inconvenient numbers. Keep everything you recorded.
Read the thresholds that will govern your count day. Oregon's heat illness prevention rules tie duties to two heat index levels. At 80 degrees Fahrenheit or above, you must keep drinking water immediately and readily available to exposed employees at all times, at no cost, according to the Oregon Secretary of State Administrative Rules. At 90 degrees Fahrenheit, higher duties kick in, which step five covers in detail.
If your readings land close to either threshold, plan for the higher level. A count that starts below 90 can drift above it when the afternoon warms. Your plan should already hold the stricter duties.
Check who on your team owns the count-day heat plan. In most shops, that is the manager or the shift lead. Name that person before the count, so nobody waits to decide when the first hot reading arrives.
Write down the plan you intend to follow: water, rest breaks, and how you will watch the heat index during the count. A short written plan keeps everyone aligned when the warehouse gets loud.
Bring your meter to a spot you can reach during the count. You will take follow-up readings while people work, so the gear has to stay close.
2. Pick a spot and a schedule for readings that match the count area
Now choose where and when you read. The heat index rules in Oregon speak about the work area. Your count area is the work area for count day. Readings from a spot far from the count zone tell you nothing useful.
Take readings at regular intervals across the count shift. Read at the start, in the middle, and near the end. If the count runs long or moves between zones, read again each time you move.
Watch for the conditions that push the heat index up. Direct sun on a loading dock raises the heat index quickly. So does a stalled fan. Record the spot conditions next to each reading so later you understand the spread.
Aim for enough readings to show a pattern. A handful of readings across the shift is fine for a small area. A large count spanning many zones needs more.
Keep your readings in one column of your sheet. One reading on each row keeps the set tidy for the next step. Mark any reading you suspect was taken with a faulty meter, but keep it in the list with a note.
If a reading seems strange, take another reading right away before you write it off. A meter held near a hot surface returns an odd number. A fresh reading confirms what you have.
If your team runs multiple count areas at once, read each area on its own schedule. The heat index in one aisle can differ from the one at the dock.
Now check your list against the first threshold. Oregon requires that when the heat index in the work area equals or exceeds 80 degrees Fahrenheit, you keep drinking water immediately and readily available to exposed employees at all times, at no cost.
The rule also sets the amount: each employee must get enough drinking water to consume up to 32 ounces per hour. Keep that supply within reach during the count. Do not stage it somewhere that takes a walk to reach.
Here is how the thresholds and the duties they trigger compare:
| Heat index in the count area | Duty your count day carries | Source |
|---|---|---|
| 80 degrees Fahrenheit or above | Drinking water immediately and readily available at all times, at no cost, enough for up to 32 ounces each hour for every employee | Oregon Secretary of State Administrative Rules |
| 90 degrees Fahrenheit or above, when controls cannot bring exposure below that level | High-heat practices and procedures, including a written rest break schedule | Oregon Secretary of State Administrative Rules |
3. Summarize the readings with three measures of central tendency
Your list of readings tells you a lot, but a single figure makes the day easier to plan around. That figure comes from a measure of central tendency. Three measures do the job for count-day readings: the mean, the median, and the mode.
Microsoft's reference for Excel's Average function defines each one plainly. The mean is the arithmetic mean, "calculated by adding a group of numbers and then dividing by the count of those numbers." The median is "the middle number of a group of numbers." The mode is "the most frequently occurring number in a group of numbers." These definitions come from Microsoft Learn.
So on your sheet, with one reading on each row, you get three figures:
- mean: add all the readings, divide by how many you took
- median: line the readings up from low to high, take the middle value
- mode: the reading that shows up most often
You can compute all three in Excel.
Which one you use depends on the shape of your readings. Microsoft's reference states that "For a symmetrical distribution of a group of numbers, these three measures of central tendency are all the same." If your readings cluster evenly around the middle, any of the three will do, and you can pick the one your team already understands.
The reference also states that "For a skewed distribution of a group of numbers, they can be different." A count area with one hot zone will skew the readings. A few very high readings pull the mean up, while the median and the mode barely move.
Here is the practical difference on a count day. Suppose your readings mostly sit in the low 80s with one reading far above the rest. The mean climbs toward that outlier. The median stays with the pack. The mode repeats the value your meter returned most often.
Any single reading at or above 80 degrees Fahrenheit in the count area starts the water duty, whatever the mean or median shows, because the summary figures do not override one crossing. Look at all three before you decide your count-day posture.
One caution on the mode with heat readings. Check your own meter's reporting resolution, since a repeat value can reflect rounding rather than a steady condition. Treat the mode as a supporting figure, not the headline number.
If they disagree, that spread is itself a signal. Something in the count area is moving the temperature, and you want to know what.
4. Read each measure against the 80 degree Fahrenheit threshold
Take your three figures and compare each to 80 degrees Fahrenheit. This step tells you whether drinking water duties are already running.
If your median sits at or above 80 degrees Fahrenheit, at least half of your readings crossed the line. Your count area has reached the threshold in substance, not just in a single spike. Any single reading at or above 80 degrees Fahrenheit in the count area requires water; the median only describes how widespread the heat is.
If your mode sits at or above 80 degrees Fahrenheit, that value came up most often.
If your mean sits above 80 degrees Fahrenheit while the median and mode sit below it, the hot readings pulled the average up. That happens when one zone runs warm while the rest stays cool. In that case, read the individual readings as well as the summary, and keep water available to exposed employees across the whole count area, including the hot zone.
The rule speaks about the heat index in the work area, so the duty attaches to the area where people actually count. Water belongs at those spots, not in an office down the hall.
Once the duty applies, it applies continuously. The rule requires water immediately and readily available at all times during that condition, not only at the start of the shift. Keep the supply topped up as the count runs.
Track how the water supply holds against the stated amount. The rule requires each employee to be supplied enough drinking water to consume up to 32 ounces each hour. Count heads at the start of the shift so you know how much water to stage.
A count area that holds heat between the dock and the storage aisles needs water staged along the path, not only at the entry. Walk your planned count route before the count and place water where people will actually stand.
Your readings will change during the count. Take a fresh reading after lunch or after a door sits open for a while. If a new reading pushes the measure back under the line, keep the water in place anyway. Moving supplies mid-count costs more time than leaving them.
If your counts and thresholds raise a question about how a specific reading applies to your area, that is a good moment to ask your supervisor or your safety contact before the count starts.
5. Read each measure against the 90 degree Fahrenheit threshold
Now compare the same three figures to 90 degrees Fahrenheit. This threshold works differently, so read the trigger carefully.
Oregon's rule turns on a situation, not just a number. When engineering controls such as fans or air conditioning, and administrative controls such as scheduling work during the cooler part of the day or limiting an employee's exposure, do not reduce exposure to a heat index of less than 90 degrees Fahrenheit, you must implement and maintain high-heat practices and procedures.
So the sequence is: apply the controls you have first. Read the heat index again. Only when the readings still do not fall below 90 degrees Fahrenheit do the high-heat duties come in.
Apply that sequence to your three measures. If your mean reaches 90 degrees Fahrenheit but the median stays below it, readings at or above 90 degrees Fahrenheit may remain in a hot zone that controls have not brought below 90, and the high-heat duties apply to employees exposed there, so add controls in that zone and read again. Run more controls where the hot readings came from and read again.
High-heat duties apply when readings at or above 90 degrees Fahrenheit remain after controls, for employees exposed in that area, not only when the median and mode both reach 90. Your controls have not moved it down. The high-heat duties apply to the count.
Fan placement and count scheduling count as controls under this rule. So does limiting exposure by rotating people through cooler zones. Use the controls you already have on site and see where the readings land.
Rest breaks are part of the high-heat package. Oregon requires a written heat illness prevention rest break schedule for employees exposed to a heat index equal to or greater than 90 degrees Fahrenheit as part of the high-heat practices, which apply only when engineering and administrative controls cannot bring exposure below 90 degrees Fahrenheit. Get that schedule written before a hot count, not while people are already on the floor.
The purpose of those rest breaks is stated in the rule: to allow the body to cool down and recover from working when the heat index equals or is greater than 90 degrees Fahrenheit. Build the breaks into the count plan so the schedule holds even when the count runs long.
The rule offers an employer-designed option: implement a written employer-specific heat illness prevention rest break schedule using the minimum rest break durations and intervals in Table 1 of the rule. Read that table before you write your schedule, since it sets the durations and intervals you must meet.
One document covers both thresholds. Put your water plan and your rest break schedule in the same written heat illness prevention plan. Keep a copy where count staff can reach it.
Re-read the heat index during the count whenever a control changes. Turning a fan off, opening a dock door, or moving the count into a sunlit aisle can shift the readings. Your measures from step three were a snapshot; fresh readings keep the plan honest.
If your area runs right at the line between the two thresholds, plan as if the higher level applies. A count that begins under 90 degrees Fahrenheit can climb past it, and switching plans mid-count costs time you do not have.
6. Record the three measures with the count pack so the next count starts informed
Your readings, your three measures, and the controls you ran belong with the count record. File them where the next count crew will find them.
Write down the three figures: mean, median, and mode. Write down how many readings you took and at what times. Note which thresholds the readings reached.
Note which controls you ran: fans, scheduling changes, water staging, and rest breaks. Note whether the rest break schedule was the employer-designed option from the rule.
That record shows the next crew what a hot count looked like in your area. They will know how readings moved across the shift and how the plan held.
Keep the raw readings too. On the next count, you can compare this shift's set against the last one and see whether a zone is getting warmer year over year.
Store the record with your count paperwork. A heat plan filed with the safety binder and never opened during a count has failed at the moment it matters.
Walk the record with your count staff at the pre-count huddle. Everyone should know which threshold applies today, where the water sits, and when the first rest break comes.
Update your written heat illness prevention rest break schedule if this count showed a gap. If people needed a break sooner than the schedule allowed, the schedule needs a change.
Keep your reference pages current. Oregon posts its rules through the Oregon Secretary of State Administrative Rules, and the Excel definitions sit on Microsoft Learn. Bookmark both for the next count cycle.
Your three measures, read against the two thresholds, turn a stack of readings into a count-day plan your crew can follow in the heat.
Related guides: California high-heat rules for count day: 5 duties · Pay for a short count-day call-in: 3 state pay checks · Stock count conditions: 3 tests before count day.