When shippers plan for cold chain risk, most of the attention goes to the voyage itself, for example how many days at sea, what route, and what what season. Less attention goes to a factor that often does more damage: dwell time, or, the period a container sits idle at a port or terminal before or after its ocean leg. In some cases, the cargo itself will sit on the tarmac while shippers change the mode of transport.
- What Is Container Dwell Time? -
Dwell time is the time a container spends at a port or terminal either waiting to be loaded onto a vessel, waiting after discharge for customs clearance, or sitting during a transshipment stop, rather than actually moving. It's shaped by terminal infrastructure and equipment, customs processing speed, and how well-connected the port is to rail and road networks. Ports with older infrastructure or high congestion tend to see longer dwell times than modern, well-equipped terminals.
Dwell time isn't fixed or predictable. Severe weather, port congestion, and rerouting around geopolitical disruptions can all extend it. In recent years (2026 especially), several major trade lanes have seen average dwell times climb well beyond historical norms as vessels reroute around conflict zones and congested chokepoints.
Dwell time isn't fixed or predictable. Severe weather, port congestion, and rerouting around geopolitical disruptions can all extend it. In recent years (2026 especially), several major trade lanes have seen average dwell times climb well beyond historical norms as vessels reroute around conflict zones and congested chokepoints.
- Why Dwell Time Is a Thermal Risk, Rather Than Just a Delay -
A container sitting still in a yard is not a container at rest, thermally speaking. Direct solar exposure on a stationary container can push internal temperatures far above the surrounding air, internal readings well above 50°C are common in hot conditions, with the interior sometimes running 15–20°C hotter than the ambient air outside.
The roof takes the worst of it. It absorbs more direct solar radiation than any other surface, so the space just beneath the roof consistently runs hotter than both the general interior air and the outside ambient temperature. Cargo stowed near the top of a container is exposed to conditions that a single mid-container temperature reading wouldn't reveal.
This matters more than it might first appear, because a moving vessel offers a natural cooling effect that a stationary port yard does not. Once at sea, a container benefits from the moderating influence of surrounding seawater, which averages a relatively stable temperature globally. A container parked in a hot yard has no access to that effect as it's fully exposed to ambient air and direct sun with nothing to temper it.
The roof takes the worst of it. It absorbs more direct solar radiation than any other surface, so the space just beneath the roof consistently runs hotter than both the general interior air and the outside ambient temperature. Cargo stowed near the top of a container is exposed to conditions that a single mid-container temperature reading wouldn't reveal.
This matters more than it might first appear, because a moving vessel offers a natural cooling effect that a stationary port yard does not. Once at sea, a container benefits from the moderating influence of surrounding seawater, which averages a relatively stable temperature globally. A container parked in a hot yard has no access to that effect as it's fully exposed to ambient air and direct sun with nothing to temper it.
- Why This Matters for Passive Thermal Protection -
Passive insulation, i.e. pallet covers, container liners, and similar products, works by slowing the rate of heat transfer, not stopping it outright. A standard reflective cover can slow the rate of temperature increase to roughly 1°C per hour even in extreme ambient heat, but that protective window is finite. Every hour a container spends sitting in a hot yard before the voyage even begins draws down that window before the "real" transit has started.
This is why total transit time alone is an incomplete way to plan thermal protection. Two shipments with identical sailing schedules can face very different cumulative heat exposure if one route runs through a congested transshipment port with several days of dwell time in direct sun, and the other doesn't.
This is why total transit time alone is an incomplete way to plan thermal protection. Two shipments with identical sailing schedules can face very different cumulative heat exposure if one route runs through a congested transshipment port with several days of dwell time in direct sun, and the other doesn't.
- What Shippers Should Ask -
Rather than requesting only total transit time from a freight forwarder, it's worth asking specifically about:
❆ Average dwell time at the origin port before loading
❆ Any transshipment stops, and typical dwell time at each
❆ Whether containers are likely to sit in direct sun or in shaded/stacked positions
❆ Destination port dwell time before final pickup
This information allows for a more accurate assessment of whether a given passive thermal solution has enough protective margin for the full door-to-door journey, not just the sailing portion of it.
❆ Average dwell time at the origin port before loading
❆ Any transshipment stops, and typical dwell time at each
❆ Whether containers are likely to sit in direct sun or in shaded/stacked positions
❆ Destination port dwell time before final pickup
This information allows for a more accurate assessment of whether a given passive thermal solution has enough protective margin for the full door-to-door journey, not just the sailing portion of it.
