Transit temperatures in the Greek summer: where a parcel heats up and what to do about it

The Greek summer does not threaten a parcel because the air is hot. It threatens it at the points where the parcel stops: in a closed van parked in the sun between two deliveries, on a loading dock in the afternoon, in a port warehouse, in a locker fixed to a west-facing wall. At the peak of the July 2026 heatwave, stations of the National Observatory of Athens recorded a maximum air temperature above 43 °C ^[1], and a closed vehicle in the sun gets markedly hotter than the air around it ^[2]. For the buyer, the useful question is therefore not "how many degrees" but "how many hours, and where".

This article stays on the domestic route: where heat builds up on a Greek courier shipment, and how the buyer limits and documents the exposure. What heat does to the material itself, and how a warm arrival should be judged, are scientific questions covered on reference sites; here we link to them rather than repeat them.

Where a parcel heats up in July and August

The temperatures weather services publish are air temperatures, measured in shade with ventilation. A parcel sits in a different environment. The best-known study of closed vehicles measured the interior temperature of a dark saloon car continuously for an hour on sunny days with ambient temperatures of roughly 22 to 36 °C: the interior rose well above the outside air, with most of the rise inside the first half hour, and slightly opened windows made little difference ^[2]. The study concerned a passenger car, not a delivery van, and its figures do not transfer. What transfers is the qualitative conclusion: a closed vehicle in the sun does not follow the air temperature, it overshoots it, and it does so quickly.

On a typical domestic route a parcel passes through five to seven such stops. None is catastrophic on its own; what matters is their sum, and whether one of them lasts much longer than the rest.

Duration of exposure versus peak temperature

A short peak while a van is unloaded is not the same event as a weekend in a warehouse without air conditioning, even if the maximum temperature is identical. For the buyer, the variable that can be controlled is duration, and duration is decided mostly by the calendar. Carriers count their times in working days ^[4], so a parcel leaving on Friday afternoon can sit at a hub until Monday and still be entirely within the published time.

Honesty is due here about what is actually known. There is no official guideline defining how the transport conditions of sensitive products should be justified; the literature says so and proposes stability studies that cover the excursion profiles expected on the route ^[5]. For most research materials, data of that kind is not published per profile. So the question for the sender is not "will it survive the heat?" but "do you have data for an exposure of this length, and if not, how have you designed the packaging and the dispatch day?". The answer, or its absence, is information.

The practical conclusion is simple: shorten the exposure rather than chase the peak. One day less on the route does more than one extra ice pack.

Why lyophilised material tolerates more than buyers assume

Most buyers picture a vial that "goes off" the moment it warms. For material in solution that is close to the truth; for a sealed vial holding a dry, freeze-dried cake the picture is far less dramatic, because for a dry, freeze-dried powder, keeping moisture out matters more than keeping the temperature down. That is not a licence for indifference: each material's tolerance is specific, depends on its composition, and belongs to the sender's data rather than to a general rule.

The arrival-day question, meaning what a parcel that arrived warm actually means, is different from the route question and is answered separately. Here we keep only the consequence for planning: because dry material has some margin, the right investment is not to spend that margin needlessly on a weekend at a hub.

When a coolant is justified

A coolant is not self-evidently the better choice. An ice pack works for a finite time; once it has melted it stops protecting and simply follows the temperature around it. Until then, on a one-day domestic route with dry material, it adds weight, bulk and a false sense of security. There is also a legal point buyers overlook: the general terms of a basic courier service do not commit the carrier to any temperature range. ELTA's terms, for example, place responsibility for safe and appropriate packaging on the sender according to the contents, and exclude from the company's liability damage caused by the perishable nature of the contents, such as food with an expiry date and medicines, where the terms of carriage were met ^[3]. Thermal protection is therefore a packaging decision by the sender, not a service of the carrier.

• Justified when the supplier states chilled storage for the material and it is shipped in a form more sensitive than a dry cake.
• Justified when the worst realistic route time, for example to an island on an infrequent route in August, exceeds two working days.
• Meaningful only if the sender knows the hold time of their packaging and it covers the route plus a possible weekend.
• Adds little for dry material travelling one working day to a mainland town, provided it does not spend a weekend at a hub.
• If the coolant is dry ice on an air route to an island, the shipment changes regulatory status; ask before you order.

What to ask the sender before a summer order

Most thermal failures on domestic shipments are not bad luck but decisions nobody took explicitly: which day the parcel leaves, with which service, in which packaging. Five questions, sent before the order, turn those decisions from implicit into written. Each answer fits on one line; no answer is also an answer.

1. Which day of the week is the parcel dispatched, and is Friday avoided for destinations with a range above one working day?
2. With which carrier and which service, so I can check whether my address is remote for that particular carrier?
3. Does the packaging include a coolant or a temperature indicator, and for how many hours has it been documented to hold its range?
4. What storage conditions are stated for the material, and what exposure in transit does the sender consider acceptable?
5. What happens if the parcel is held at a hub or a port: am I told, and who decides what happens to the shipment?

None of these questions requires scientific knowledge from the buyer. They only need to be asked before payment, while the sender still has every reason to answer precisely, and filed with the order.

Documenting the route

International guidance on good storage and distribution of medical products asks that required conditions be maintained in transit, with monitoring and recording where a risk assessment of the route calls for it ^[6]. Research material does not fall within that framework, but its logic transfers intact: an excursion that was never recorded can never be assessed. For a small recipient without a data logger, the most complete thermal record is something they already hold: the tracking history, where every scan is a place and a time.

1. Before ordering: note the destination zone, the dispatch day you asked for, and whether the packaging includes a coolant or a temperature indicator.
2. At dispatch: save the tracking number and the time of the first scan.
3. In transit: keep a screenshot of the tracking history before it is archived, with the time of every scan; note every night or weekend spent at a hub.
4. On arrival: record the delivery time, the state of the coolant and the reading of any indicator before moving anything.
5. File all of this with the batch number, so it travels with the material rather than with the order email.

With that in hand, the question to the sender becomes specific: not "it arrived warm", but "it spent forty hours at a hub in early August and the ice packs were liquid on arrival". That is the material every serious answer about how a temperature excursion is assessed on receipt starts from, and the only part that cannot be reconstructed afterwards. The rest of the arrival check is set out in the goods-in checklist.