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Weather Working Days

Member Advisory

Even the most clear cut, fixed laytime regimes agreed in a voyage charter can still give rise to disagreement – whether it be about when a vessel became an arrived ship, whether a particular load rate was achieved, or whether or not an interruption has been properly credited in a laytime calculation. However, this is made infinitely more complicated where parties agree to a laytime regime by reference to, for example, weather working days.

The definition in English law of what constitutes a weather working day is straightforward: it is a day on which the weather permits the relevant work to be done. Whether any cargo operations are carried out is irrelevant; as long as the weather does not prevent those operations from taking place, laytime counts.

The essential issue is therefore the character of the day (i.e. whether or not any adverse weather was experienced) and not whether work was actually interfered with (Reardon Smith [1963] 1 LLR 12, at p41). This extends also to any periods after the vessel has become an arrived ship but before having berthed. In other words, if the prevailing weather conditions would have permitted the vessel to be worked, had she been in berth, laytime counts. Conversely, any periods during which adverse weather would have prevented working of the vessel in berth are excluded from the laytime calculation.

Where matters become a bit more complicated and contentious is in relation to: (a) what constitutes weather for the purpose of interrupting laytime; and (b) evidence of those weather conditions.

What constitutes weather for the purpose of interrupting laytime

Largely, this is a factual question and is dictated by the type of vessel and the type of cargo being carried. For example, for a dry bulk vessel carrying sugar in bulk, rain would constitute bad weather but for a crude oil tanker, it would not. In addition, the weather must be adverse to cargo operations and not some other operation.

The usual type of adverse weather experienced consists of heat, rain, fog, hail, snow and sleet, high winds, and the immediate consequences of such atmospheric conditions; it does not include indirect consequences. Frost and ice can also interfere in cargo operations being carried out, due either to machinery being rendered in operable or cargo being exposed to the risk of damage.

High swell might also constitute adverse weather if, for example, the vessel is at anchorage and it prevents lightering operations from being carried out. However, ideally, what constitutes "high" swell should clearly be spelled out in the charterparty to avoid any disputes as to whether the swell was sufficiently big to qualify, or whether it rendered the anchorage unsafe and the concerned period therefore counts as laytime (see Laytime WWD (Weather Working Days) for guidance on this point).

Any other specific weather phenomena that might be experienced at a particular port should, ideally, also be clearly stated in the charterparty. This is because a particular port might experience an unusual weather phenomenon, which might not usually be experienced at other ports. Unless dealt with expressly in the charterparty, such weather phenomena could well fall outside the contemplation of the parties' understanding of adverse weather and give rise to heated discussion whether it should be excluded from laytime.

It is therefore highly advisable to clearly and unequivocally set out in the charterparty what should be included or excluded as adverse weather, as this will avoid contentious, frustrating, and frequently lengthy and costly disputes on this issue.

Evidence of weather conditions

There will, of course, be a natural conflict between owners and charterers as to which evidence will form the basis of assessing weather conditions locally. Owners, naturally, will prefer the vessel's logs and/or the Statement of Facts prepared by the Master as evidence of the weather conditions. The charterers, on the other hand, will often prefer their own source of information to form the basis of the evidence, such as, for example, a Statement of Facts prepared by their Agent.

If no provision is made as to which set of weather data will prevail, instances may arise, for example, where a vessel is at an outer anchorage where the weather experienced differs from the weather in berth. This problem is compounded if lightering operations are conducted at the outer anchorage. The competing evidence might differ significantly in those circumstances.

This type of conflict can be avoided in several ways; namely, by clearly stating in the charterparty:

(i) That the evidence of the weather conditions will come solely from one source (e.g. the Master's SOF will be determinative); alternatively

(ii) That evidence of the prevailing conditions will be taken from multiple sources but that a comparison will be made of the weather days and, in the event of inconsistencies, one party's evidence will prevail (for example, the stevedores' timesheets will prevail over the Master and Agents' SOFs); alternatively

(iii) That an independent third party (appointed with the agreement of owners and charterers) will produce a weather report, which will form the basis of the laytime calculations.

It should be noted that there will not always be weather data available from third parties at certain ports, or such weather data might unreliable as the weather station recording that data is too far away from the berth or anchorage to considered as an accurate reflection of the conditions experienced by the vessel.

Careful consideration should therefore be given as to which of the above options is the most reliable source of weather data for a particular port. Accordingly, a clause in a previous charterparty might not be suitable to simply be cut and pasted into a new charterparty. The clause might therefore need to be amended to avoid situations where, for example, a weather company is named but has no offices at the ports under the new charterparty.

Calculation of weather interruptions

Once a clear determination has been made as to what weather periods are excluded from laytime, based on the agreed terms of the charterparty and in accordance with the weather data, the final step is to properly prepare the laytime calculation. The method for performing this calculation has previously been discussed in a recent article Laytime WWD (Weather Working Days).

It should be noted that, once laytime has expired and the vessel is on demurrage, even if there are periods of adverse weather during that time, such periods do not have the effect of interrupting demurrage. Once on demurrage, the vessel remains on demurrage. The only way to avoid this result is if very clear and unequivocal wording is used excepting adverse weather from counting against demurrage.


As will be apparent from the above, what constitutes a weather working day is relatively straightforward.

What gives rise to conflict, however, is competing views of what constitutes adverse weather, and whose weather data should be used to assess whether the weather was adverse for the purpose of laytime.

With the use of a little forethought, and clear and unequivocal wording in the charterparty, most of these sorts of disputes can be avoided.

And, if ever in doubt as to what kind of wording to use in the charterparty, feel free to contact us to have a chat or to assist with drafting.


Ollie van der Zee

Claims Executive, Lawyer
Direct: +65 6438 8010 Mobile: +65 9658 8568 E-mail: