The Final Forty-Eight Hours of a Shipment: Where the Heat Actually Happens

The companion piece on courier hubs and routing explains how long a parcel takes to reach an African destination and why two neighbouring countries can differ by a week. This article asks a different question: what conditions the parcel sits in while that time passes. For most consignments the answer is that the long legs are the mild ones. Flights are short relative to the whole journey and hub sorts are measured in hours. The heat arrives in the final forty-eight hours, after landing — in a customs holding area, on a depot floor between sort and delivery, in a van on a daytime round, and in a second depot night if the first delivery fails. None of those intervals appears on a waybill.

That makes the last leg the one part of the journey a buyer can actually influence. Transit time is set mostly by the network and the border. The conditions of the final two days are set, to a surprising degree, by when the order was placed, how the delivery point was written and whether anyone answered the phone. What follows walks the leg in order and ends with the levers you hold.

Why the last leg dominates cumulative exposure

Heat exposure is a product of temperature and time, which is why every formal method for judging an excursion asks both how hot it got and how long it lasted, and treats transport as its own window running from despatch to arrival ^[5]. On an intercontinental routing the time is not spent moving. A consignment that lands on a Friday afternoon, clears on Monday and is delivered on Tuesday may have spent twelve hours in the air and several days on the ground at the destination end. It is the ground time that fills the record.

The WHO method for profiling a transport route is built around exactly this. It asks for ambient temperature to be logged every ten to thirty minutes, with a checklist recording entry to and exit from each critical control point — loading a truck, entering a warehouse — so that the temperature trace can be tied to specific events along the route ^[1]. It asks for sampling across the hot and cold seasons, and it notes that a small parcel does not necessarily experience the same thermal environment as a palletised load ^[1]. Research consignments are almost always small parcels, which is the category least protected by the thermal mass of the goods around it.

The best published measurement of ordinary small-parcel networks makes the point from the other direction. Researchers who sent logger-equipped packages between three US states, using different carriers and shipping methods in both winter and summer, found that the packages spent on average 68.3% of transit time outside the controlled room temperature range ^[4]. That is a temperate country with mature, well-documented networks. For a hot destination it is a floor, not a ceiling.

Customs holding areas and their conditions

Arrival at the destination gateway starts the least visible interval. A consignment awaiting clearance sits in a bonded area or transit shed controlled by the carrier or a ground handler, and its conditions are those of the building. WHO's guidance on temperature-controlled transport by road and air treats the airport apron as a critical handling step requiring minimal time at ambient temperature, high-priority ramp handling and covered storage, and for warehousing en route it expects temperature monitoring, defined storage instructions and defined actions in the event of delays ^[2]. Those expectations attach to shipments declared and booked as temperature-sensitive. A standard express parcel carries no such instruction, so none of them applies by default.

The length of the hold is the variable that matters. The World Bank's 2023 logistics index, drawing on air cargo tracking data, found average import dwell times ranging from well under a day in the fastest economies to close to ten days in the slowest ^[8]. A clearance query raised on a Friday is, at many gateways, a weekend in a shed. The same WHO guidance also notes that doors may have to be opened for customs inspection ^[2]. For an insulated shipper, a lid lifted in a warm inspection area is an exposure event that no document will mention.

Local depot storage between sorting and delivery

Once released, the parcel moves to a delivery depot and waits for the next round — usually overnight, sometimes over a weekend. Depots are built for vehicle access and throughput, not for holding conditions, and the companion article on warehouse and depot conditions covers what those buildings are and are not controlled for. The point here is arithmetic: a depot night in the hottest month of the year is twelve or more hours at whatever the roof and walls allow, and it is repeated in full for every failed delivery attempt.

Regional heat is not an abstraction in these months. In late March and early April 2024 maximum temperatures across the Sahel exceeded 45 °C, with Kayes in Mali recording 48.5 °C on 3 April and minimum temperatures of 32 °C in Burkina Faso; power cuts occurred in many of the affected countries during the same episode ^[6]. A building that depends on grid-powered cooling is only as good as its holdover when the supply fails, and in a heatwave the supply is under the most strain.

Vehicle interior temperatures during daytime delivery

The delivery vehicle is usually the hottest place a parcel ever sits. Measurements in a closed, dark-coloured car on sixteen clear days found the interior warmed by an average of about 1.8 °C every five minutes, with 80% of the rise in the first thirty minutes. Across outdoor temperatures of roughly 22 °C to 36 °C the interior ended the hour, on average, more than 20 °C above the outside air, and even on the coolest day it reached about 47 °C. Leaving the windows slightly open made no meaningful difference ^[3].

A parcel van is not a passenger car, and a windowless load space is shaded from direct sun. The mechanism is the same, though: solar gain on a closed metal body, repeated at every stop on a daytime round. WHO's guidance for passive shipments by road asks for covered vehicles so that shipments are not exposed to the sun, and for vehicles to be parked in the shade during stops wherever possible ^[2]. Neither is something a standard parcel service promises. Plan on the assumption that the afternoon round is the harshest hour of the whole journey, because for most parcels it is.

Failed first delivery and what a second attempt costs in exposure

A missed delivery does not simply delay a parcel; it re-runs the least controlled part of the journey. WHO's model guidance for time- and temperature-sensitive products rests on responsibility being defined at every stage of storage and distribution, handovers included ^[7]. A failed attempt is a handover that did not happen, followed by a holding step nobody specified. The companion article on delivery where addresses are informal explains why attempts fail; the exposure consequence is the reason to take it seriously.

• A second daytime round in a closed vehicle, with the same solar gain as the first.
• A second night on a depot floor, or a whole weekend if the first attempt fell on a Friday.
• A public holiday, where one intervenes, adding a day that appears on no document.
• An interval that no scan records — tracking shows the attempt and the redelivery, not the conditions in between.

Measured in exposure, a failed first attempt can double the final leg. Measured in evidence, it creates a gap in the record precisely where the heat was.

Reducing the window: timing, addressing, availability

None of the conditions above can be changed from the buyer's desk. How many of them a parcel meets, and for how long, can. Four practical levers, in order of how much time they usually save:

1. Timing. Place the order so the consignment reaches the destination gateway early in the working week, not on a Thursday or Friday, and not before a public holiday. In the hottest months of your region, give that rule priority over speed.
2. The delivery point. Nominate a branch counter or an institutional receiving bay with published hours rather than a doorstep. A known node turns an uncertain round into a collection you control, ideally in the cool of the morning.
3. Availability. Give a named receiver and two reachable numbers, and answer unknown numbers on the days the consignment is in the country. A delivery that succeeds first time removes the second round and the second depot night.
4. Evidence. Ask for a temperature logger in the consignment and read it at receipt. WHO's transport guidance expects the consignee to retrieve and download the monitors and attach the data to the arrival record ^[2].

The logger produces evidence, not a verdict. Whether a recorded warm leg matters is the job of a receipt-side excursion assessment, and for dry material the honest answer is often less alarming than the moment feels — the reference network sets out what a warm spell in transit actually does to freeze-dried material. This article stops at where the heat comes from.

What the evidence does not tell you

No published route profile exists for a small parcel's final leg into an African city. The route-profiling method is public and repeatable ^[1], the vehicle measurements come from one careful study in a temperate summer ^[3], and the best small-parcel dataset describes a different continent ^[4]. What those sources establish is the shape of the problem — ground time dominates, vehicles are the peak, failed attempts repeat the worst hours. The magnitude on your own route is something only your own loggers will tell you, and five shipments of your own data will be worth more than any figure quoted here.