How to do temperature logs correctly
By Vimal Bhaya, Founder and Lead Systems Architect · Last reviewed 21 October 2026
This is part 1 of 4 in Temperature log basics, a short tutorial on keeping temperature logs that hold up.
Take a real reading with a thermometer you have checked, in the warmest part of the box. Write it down straight away, with the time, the unit, your initials and what you did if it was out of range. Then make sure someone reads the log every day.
Under the FDA Food Code, cold food has to stay at 41°F (5°C) or colder and hot food at 135°F (57°C) or hotter. A log is the record that shows it did, between one inspection and the next. It only works if every number in it was actually read.
Every entry needs seven things
A log is a list of entries. Each one has to stand on its own, so that someone reading it a year later knows what was checked, when, by whom, and what happened next.
| Part | What to write | Why it matters |
|---|---|---|
| Date | The day of the check | Logs get filed, and pulled out months later |
| Time | The time you took the reading, not the time slot printed on the form | A 3 PM check done at 4:10 PM says so |
| Unit | Which cooler, freezer or hot holding unit | One sheet usually covers several boxes |
| Reading | The number on the thermometer, with °F or °C | Not rounded, and never the target printed on the form |
| Initials | Of the person who took the reading | Whoever wrote it can be asked about it |
| Action | What you did, if the reading was out of range | A high reading with nothing beside it looks ignored |
| Checked by | Initials of the person who read the log that day | Shows that someone looked |
The Food Code sets the temperatures, not the layout of the sheet. The layout above follows what federal rules ask of food plant records: the actual value, the date and time, and the initials of the person who did the check, written when it was done (21 CFR 117.305). A state school log asks for the same: "the date, time, air temperature, corrective action, and initials", with the manager reviewing it "each working day".
Check the thermometer before you trust it
A log is only as good as the thermometer behind it. The Food Code requires food thermometers to be accurate to within 2°F, or 1°C on a Celsius scale (4-203.11). The ice-water check takes two minutes:
- Fill a glass with ice, then top it up with cold water. Stir, and let it sit for a minute.
- Put the probe in the middle of the glass, not touching the sides or the bottom, and wait for the number to settle.
- Should read: 32°F (0°C). If it is off, adjust it if it has a calibration nut or button. If it cannot be adjusted, replace it.
- Write the check down, with the date, the reading and your initials.
A thermometer that has been dropped gets checked again before it is used. How electronic sensors drift, and what actually spoils them, is in sensor accuracy, drift and calibration.
Measure in the warmest part of the box
The Food Code says the thermometer in a fridge or freezer goes in "the warmest part" of the unit (4-204.112). School kitchen guidance says the same for checking a cold holding unit by hand.
- For the box, read the thermometer in the warmest place where food actually sits. Not right under the coil, where the coldest air comes out. Where to put a sensor in a walk-in explains why the coil flatters the box.
- For the food, push the probe into the thickest part, which is usually the center.
- If you read the display on the front instead, say so on the log, and always use the same one.
Air changes faster than food. A door left open warms the air in minutes, while a full tray takes far longer. If the air reads high, probe the food before you decide anything. Glycol buffers and thermobuffers shows the difference on real readings.
Write it down when you take it, and write what you saw
- Write each round as you go. Fill the column for this check across every unit, then stop. Never fill boxes for checks that have not happened yet.
- Write the number you read. 39.6 is 39.6. A log full of round numbers that match the target is a warning sign, not a good log.
- Use pen. The federal rule for food plants says records must be "accurate, indelible, and legible".
- Correct a mistake with one line. Strike it through once, write the right number beside it, and initial it. Never white it out.
- Never make up a missed check. Leave it blank and write why. A blank with a reason is honest. A made-up number is what the trade calls pencil whipping.
A reading out of range needs an action written next to it
When cold food or a cold box reads above 41°F (5°C), school kitchen guidance from the Institute of Child Nutrition sets out what to do:
- Probe the food in its thickest part, to see whether the food is warm or only the air.
- Chill it fast if it was fine 2 hours ago. If the last reading at or below 41°F (5°C) was within the last 2 hours, rapidly chill the food: a blast chiller, an ice water bath, or smaller, thinner portions.
- Throw it out if you cannot tell how long. Food goes in the bin if nobody can say how long it was above 41°F (5°C).
- Fix or reset the box before food goes back in.
- Write down what you did, next to the reading.
Do not put food back into a box that has not come back to 41°F (5°C) or colder.
If the box itself is the problem, walk-in cooler troubleshooting and reach-in cooler troubleshooting go through the causes one at a time.
Someone has to read the log every day
The Food Code makes the person in charge responsible for "daily oversight of the employees' routine monitoring of food temperatures" (2-103.11). In practice, that means reading the log before the shift ends:
- Look for blanks, and find out why they are there.
- Look for high readings with no action next to them.
- Look for numbers that never move. A box that reads the same at every check is more likely a check nobody took.
- Initial the log once you have read it.
Who does each part is set out in who is responsible for temperature logs, and how long to keep the sheets afterwards in how long to keep temperature logs.
TemperatureWise records the hours between the rounds
A log taken by hand is a few snapshots a day. TemperatureWise records each box at least every 15 minutes, day and night, and keeps the record indefinitely. When a box drifts out of its normal pattern, it emails, then texts and calls until someone answers.
It does not replace the people. Staff still check thermometers, still probe food when they cook, cool and receive it, and still write down what they did about a high reading.