How to Read a Temperature Log and Spot Excursions

What It Means

A temperature log is a continuous time-stamped record of interior trailer temperature throughout a shipment. Temperature loggers — small electronic devices placed inside the trailer at loading — record at intervals ranging from 5 to 30 minutes and produce a downloadable report at delivery. The log tells you exactly what the product was exposed to during transit, when, and for how long.

An excursion is any recorded period where temperature moved outside the specified acceptable range. Excursions range from minor and inconsequential to critical and product-compromising. The difference is defined by the product's Mean Kinetic Temperature (MKT) tolerance and the duration, magnitude, and timing of the excursion relative to overall transit.

Why It Matters

• Temperature logs are the primary evidence in any product quality dispute or insurance claim related to a cold chain shipment
• Without a log, you cannot distinguish between carrier-caused damage and pre-existing product condition at loading
• Pharmaceutical products often require formal excursion analysis before the product can be released or destroyed — a log is not optional
• Cannabis QA teams use temperature logs to support or contest distributor quality holds
• Knowing how to read a log means knowing whether a finding represents actual product risk or a minor deviation with no practical consequence

How It Works

What a Temperature Log Shows

• Timestamp of each recorded data point (typically every 5, 10, or 30 minutes)
• Interior trailer temperature at each recording interval
• Any alarm triggers (typically at pre-set upper and lower limits)
• Logger start time (should match or precede loading) and stop time (should match or follow delivery)
• Summary statistics: minimum temperature, maximum temperature, average temperature, and sometimes Mean Kinetic Temperature

Identifying an Excursion

Compare recorded temperatures against the specified acceptable range for the product. Any data point outside the range is a potential excursion. Focus on: the magnitude of the deviation (how far outside range), the duration (how many consecutive readings), and the timing (early in transit when product is still at set point vs. late when product has been conditioned).

Assessing Severity

• Brief excursions (1-2 readings) at low magnitude during door openings at delivery are typically inconsequential
• Sustained excursions (multiple readings over hours) in the middle of transit are significant regardless of magnitude
• Excursions during pre-cooling phase (before or at loading) indicate the trailer was not adequately pre-cooled
• Excursions with alarm triggers that were never resolved indicate a refrigeration unit failure without proper escalation
• Consult your QA team or product manufacturer for MKT-based assessment of pharmaceutical or cannabis excursions

Common Challenges

• Logger not started until after loading, creating a gap in the pre-cooling verification record
• Logger placed near the refrigeration unit rather than in the load, recording unit output rather than product temperature
• Missing logs — carrier claims tracking occurred but no logger data is provided at delivery
• Misinterpreting door-opening spikes as product-impacting excursions without accounting for duration and recovery
• Not knowing the product's acceptable range and therefore being unable to evaluate the log at all

Best Practices

• Specify logger placement in your transport SOP — mid-trailer, mid-height, away from the refrigeration unit and doors
• Start the logger before loading and confirm start time is recorded on the bill of lading
• Retrieve the logger at delivery — do not rely on the carrier to deliver the data
• Know your product's acceptable temperature range and alarm thresholds before reviewing any log
• For pharmaceutical and cannabis products, have a written excursion evaluation procedure before you ever receive a log with a finding
• Archive all temperature logs with the associated transport record and POD

When to Use This Service

• Any temperature-sensitive shipment where product integrity at delivery must be documented
• Pharmaceutical and cannabis shipments where regulatory compliance records require temperature evidence
• Fresh produce shipments where shelf-life at delivery is the basis of buyer acceptance
• Any shipment where insurance coverage for temperature damage depends on documented excursion evidence