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How to assess your weather risk exposure?

Assessing weather risk exposure is notoriously difficult. Weather itself is an incredibly chaotic system, so it’s no wonder it’s hard to understand and assess.

In this article I’m going to highlight that assessing weather risk is actually much easier than you might think and can bring useful insights to your project that will increase your margins and help you avoid downtime.

What we will have to do first though, is unpick some of the assumptions that get made around weather, weather risk, weather forecasting and realign with what is possible today.

Forecasting the weather


For starters most people get frustrated when the weather forecast is wrong or inaccurate. This is understandable. We have giant supercomputers working day and night alongside meteorologists to calculate what the weather will be and when. Surely, we can get it right?

Forecasting weather is predicting the future, and doing it accurately requires millions of inputs on an ongoing basis to get it right. We have this today, and forecasts are generally pretty good, but we don’t have sensors in every corner of the earth, and so even minor changes in one part of the system where we have a blind spot could have a cascading effect.

It’s not just millions of data points we have to collect, humidity, temperature, wind speed etc. We also have to calculate how each of these interact with each other. It’s complex, but we are getting better all the time.

Assessing weather risk though is not the same as forecasting. We are not interested in knowing exactly what the temperature could be on a specific morning.

We just want to know if it will be 5 degrees and rising for our concrete pour, or not. With this type of output we can have much greater confidence of being correct.

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Weather risk in construction

So, if we want to assess risk properly, we need to know what we are doing, as clearly different construction activities are impacted differently than others. Painting outside is highly susceptible to humidity and rainfall, whereas painting inside is not.

When assessing weather risk exposure, it's important to first know what activities you are undertaking, and which are high risk. These activities will have thresholds at which it is appropriate, safe or feasible to work and thresholds where it is not. Some may also have a grey area, where you probably can work, but you are unlikely to be working at full capacity and if it were to get any worse you would likely stop immediately.

There are also some activities that will have no impact at all. It’s useful to know what these are and how they interplay, or depend, on other weather sensitive ones. It's possible that some of these could be undertaken at the same time as weather sensitive ones, allowing progress to continue even in poor weather conditions and therefore reducing your exposure.

The trickiest activities to think about are those that aren’t high risk, but also still carry some. Most of the time these will have unknown unknowns which could throw a spanner in the works. It might also be that there are lots of activities with small impacts which over time can eat into project margins and end up causing as much delay as a riskier activity. Mapping these is a challenge but can be vital.

construction weather risk

Combining weather data & construction knowledge


Combining weather data and your construction knowledge about how these activities are impacted is the first step to assessing your exposure. In the long term you may want to collect historical records that will highlight what weather, in a certain location, has done in the past.


Met Office

From the Met Office you can get some basic PDFs that will tell you how many lost days could be expected and what severe conditions might look like. This is broken down on a monthly basis and allows you to put a time risk allowance into your bid.

This however is a pretty poor assessment of weather risk exposure. It provides no indication of what activities will be impacted and the knock-on effects on your programme. It will at best justify a TRA to you and your client. This could be over or under what the reality will be.

This is made worse by the fact that they will provide data for a specific named weather station rather than your exact location. You get the benefit of knowing the data is accurate, but only for that location. Even small distances can cause huge differences so this and the lack of granularity offers a huge margin for error to this type of assessment.

Raw Data

The second alternative would be to download raw data for yourself and to pull this into excel. Here you would need to aggregate years of data to get some outputs that align on a daily, weekly or monthly time frame. This can usually take a day or two of wrangling to get it in shape but it can be done.

Using excel of course might lead to errors but if you are very careful then you can get the output you need. This would be better than the Met Office output as you would have greater visibility on which days are likely to experience what weather conditions and this can assist in planning to minimise these effects.

It would still likely have limitations as to the location of the data and it would still not necessarily be integrated with your planned activities.


Modern Risk Management Tools

The Best and simplest method is to leverage a modern weather risk management platform like EHAB. This tool pulls data automatically from your exact location using Artificial intelligence and Machine learning to accurately adjust historical records. It then runs climate analysis on this data to get realistic projections of weather going forward. 

You are able to directly upload your plan to the system so that every single activity is matched and assessed. Within the platform there are heavy mathematical formulas that determine exposure on each activity, and through the critical path and dependency links it can then assess your overall exposure.

You are also able to edit the plan to minimise exposure, therefore giving you a clear way to increase margins and give yourself a greater buffer for your project.


Exposure is determined by you, sometimes

Ultimately the more foresight you can get the greater your ability to deal with weather risk will be. Exposure is linked entirely to how you plan, so if you can plan more effectively then you will reduce exposure. In some cases though plans change.

If there have been other kinds of delays or even a wetter autumn than planned, then you could be facing having to concrete or do earthworks in winter. Knowing whether it’s worth soldiering on in the worsening conditions or simply delaying until after winter is not an easy task to take on.

If you are using excel or the met office for your weather assessment data then you are unlikely to have time to complete the assessment or you won't really have enough data to make a decision. These days, when there are so many opportunities for a project to go awry, the only way to assess weather risk accurately and in real time is to leverage a modern weather risk management platform.

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Assessing weather risk exposure through your project lifecycle


1. Pre-tender

a. Initial dataset review: At the very start it's useful to have overview info about flooding and other key metrics.
b. Quick assessment based on common project activities: In an ideal world the client would run a full assessment to understand the best start date to set the project up for success.

2. Tender

Full plan assessment: Getting an accurate reading for time risk allowance at this stage is important for client and contractor.

a. For the contractor this will determine their margin in relation to weather.
b. For the client this gives them a realistic expectation of potential delay.

3. Planning

Ongoing plan assessment: As the plan gets more detailed than it’s important to keep running weather assessments to ensure you are building your programme optimally.

a. Mitigation plan: In most cases you will have to present and justify weather mitigations alongside the costs of this. Knowing the cost benefit of these mitigations alongside the alternative scenario will help determine the right course of action.

4. Construction

Weather integrated short term planning: Knowing what the weather is doing and if this will allow certain activities to go ahead will be key in keeping the project on track.

a. Reassessment: Programmes shift all the time. It will be essential to re-run analysis to make sure the plan remains optimised, especially if being pushed into seasons with worse weather conditions.

5. Operation

Maintenance scheduling: Long term and short-term forecasting will determine when you can conduct regular maintenance.

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