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Weather and Construction: The Contract

 In the following post, John Crane continues our series on Weather and Construction.

The Contract

In this Ideas & Insights, I will hopefully demonstrate that by providing the proper information and guidance in the contract documents, many common issues concerning weather can be eliminated.  Two examples of standard contract language are shown below to illustrate the questions that sometimes exist in a contract.

The 2007 edition of the AIA-A201 standard agreement states:  If adverse weather conditions are the basis for a Claim for additional time, such Claim shall be documented by data substantiating that weather conditions were abnormal for the period of time, could not have been reasonably anticipated and had an adverse effect on the scheduled construction.

And, the recently issued ConsensusDOCS states:

6.3.1  If the Contractor is delayed at any time in the commencement or progress of the Work by any cause beyond the control of the Contractor, the Contractor shall be entitled to an equitable extension of the Contract Time.  Examples of the causes beyond the control of the Contractor include…adverse weather conditions not reasonably anticipated; encountering Hazardous Materials…

These clauses leave us with the question of what is considered to be “abnormal” or could have been “reasonably anticipated.”

How Do We Determine What Is “Normal?”

Whether I am an owner wishing to eliminate such questions or a contractor wanting to determine the number of “reasonably anticipated” weather days I need to plan for, there are references, such as data available from the National Oceanic and Atmospheric Administration (NOAA), that provide historical data that can be used to establish “reasonably anticipated” weather for nearly any specific region of the United States.  Another reference may come from historical project data that has been accumulated by the contractor or owner that can be used to support its calculation.  In actuality, using past project history to establish the “norm,” may be more accurate than using the data provided by NOAA.  However, not many owners or contractors have this historical information to draw upon.However, converting from averages to a finite number of anticipated weather delays must also take into account factors beyond that represented in the historical weather data, such as, (a) the type of work and materials on the project, (b) the location of the project, and (c) all the different types of weather conditions that can occur during the project period.

Some of the information provided, from such a source as NOAA, is represented as an average weather occurrence for a particular time period.  Examples of this may be an average of 0.05 inches of rain on a specific date or an average of 10 inches of rain for a specific month, all of which is based on 30 years of data.  However, converting directly from 30 year averages to a specific number of “reasonably anticipated” weather days is virtually impossible and is simply a guess.  If one were to use historical weather data to determine the “reasonably anticipated” weather days, they will need to look at the actual data recorded for each day in previous years that the project is planned.  This will allow one to determine the “norm” for any number of previous years that can then be averaged or weighted to determine the most “reasonably anticipated” weather days for the upcoming project.

If the 30 year averages are used, rather than the average number of “reasonably anticipated” weather days for previous years, the amount of average weather occurrence for any given day will most likely be minimal and the contractor could never anticipate losing a day.  For example, the following charts show the differences between the 30 year average of precipitation for the month of January recorded for Morgantown, WV, versus the actual precipitation recorded for the month of January in 2010 and 2011:



In order to come up with a number of “reasonably anticipated” weather days, one must also take into account factors beyond that represented in the historical weather data, such as, (a) the type of work and materials on the project, (b) the location of the project, and (c) all the different types of weather conditions that can occur during the project period.  Only after careful consideration of such factors can the owner and contractor reasonably estimate how and to what extent (finite number of lost days) each type of weather condition might affect work on the project.  For example, the type of soils being worked can influence how much rain it will take to make the soils unworkable, and possibly how long the soil will take to dry out so that it can be workable.

To illustrate how this would factor in when using historical weather data, let’s presume that it was predetermined that the soils would be unworkable if 0.25 inches of precipitation occurred on any given day, using the 30 year averages shown above for the month of January in Morgantown, WV, one would not have anticipated any days of delay.  However, using the actual from 2010 and 2011, one could have reasonably anticipated losing an average of two days ((1 day in 2011 + 3 days in 2010) / 2 months = average of 2 days for the month of January).

Similarly, cold temperatures, lightning, or high winds during a workday may stop progress on specific activities.  An organization such as NOAA does not provide data that will allow one to determine delays due to such events.  It will be up to the contractor and owner to discuss whether or not such delays should be included in the “norm” and to what extent.  If there is no understanding between the owner and contractor on what exactly is to be included in the “reasonably anticipated” weather days, both parties may have difficulty, after the fact, establishing that such events as dry out time should or should not have been “reasonably anticipated.”

Yet another set of questions arise when considering such things as hurricanes, named storms, floods, and the like.  However, these may qualify as Force Majeure events in the contract, and thus may not be dealt with under the standard weather provisions of the contract.  Also, any designated shutdown periods identified in the contract, such as holidays or winter closures, can be factored into the project schedule, via the schedule calendars, which is discussed later in this article.

What if the number of “anticipated” weather days has been specified?

Once the number of days representing the “norm” has been established, it is still necessary to identify how and when the days are to be tracked or evaluated during the project.  This means that the contract should identify the frequency at which the contractor is required to compare the actual number of weather days versus the number of “reasonably anticipated” weather days, for the purpose of evaluating weather-related time extension requests.  For instance, if the contract states that anticipated weather delays are to be evaluated on a monthly basis, it is important that the contract also indicate what happens to any anticipated weather days that were unused at the end of each month.  To illustrate, consider the following example.

The project has a planned duration of six months (January through June).  Historical monthly weather data was used to develop the reasonably anticipated weather days set forth in the contract and shown in the following chart:

Month Anticipated Weather Delays
January  2
February  2
 March 3
April 4
May 5
June 4
Total 20

Now assume that the contract stated that weather issues were to be tracked on a monthly basis.  Assume further that, as the project progressed, the critical path of the project was delayed by 4 days in January due to heavy rains.

Because the table above told the contractor to anticipate 2 “weather days” in the month of January, it would appear that the contractor would be entitled to a 2-day time extension.  But, what if during the remainder of the project duration, there were zero days lost due to inclement weather?  Would the contractor still be due a 2-day time extension?  Provided another scenario, what if the number of actual weather delay days in January was zero?  What would happen to the 2 unused days?  Would they carry over to subsequent months, or are they lost, leaving 18 days of anticipated weather for the remainder of the project?

The contract will need to consider and address how these provisions are to be applied and administered; otherwise, there is the possibility of multiple interpretations.

What if the contract specifies average units of weather rather than days?

Some contracts attempt to deal with anticipated weather delays by using an average measurement of a particular type of weather occurrence rather than identifying the “norm” in number of days.  And, if that average measurement is exceeded, a time extension may be due.  For example:

The contract states that the contractor may request a time extension if the rainfall at the jobsite exceeds the monthly average by 20 percent.

Although this approach defines the total amount of rainfall that must occur before a time extension is granted, it does lack clear guidance as to how many “reasonably anticipated” weather days the contractor should allow for in the project schedule and how and when the “anticipated weather” days will be evaluated for any time extensions.  According to how this particular clause is written, it appears that the “reasonably anticipated” weather would be evaluated at the end of each month and time extensions provided accordingly.

Provided with such a clause, a contractor would still need to determine a finite number of “reasonably anticipated” weather days for each month to include in the project schedule.  This can be accomplished in the same manner described at the beginning of this article.  For instance:

Assume that the project is a road project and tests show that the soils would become unworkable if the rainfall at the site equaled 0.25 inches or more.  Assume further that the historical data for the project’s location (Morgantown, WV) showed an average rainfall of 2.81 inches for the month of January.

Based on the actual historical data for January 2010 and 2011,

the contractor could reasonably have anticipated that it would be delayed an average of two days during that month.  And, therefore, would need to build those two days into its planned duration.  However, since the contractor would not receive a time extension until the monthly average rainfall (2.81 inches) was exceeded by 20%, the contractor may want to increase the amount of “reasonably anticipated” weather days by the same ratio.  Thus, the contractor may want to allow for 3 days (2 days + 20% = 2.4 days) in its project schedule to ensure it has allowed for the additional 20% that it would not receive a time extension for.

Typically, prior to bid, the owner has already set the overall duration or end date of the project.  Therefore, it is suggested that the owner understand how the monthly averages it has stipulated in the contract equate to a finite number of “reasonably anticipated” weather days, along with any other days it feels should be included and allowed for in the project schedule as part of the “norm.”  The question as to whether or not the contractor would be allowed to carry over any unused “reasonably anticipated” weather days from January still remains with such a clause.

What If The Contract Is Silent With Respect To “Anticipated” Weather Days?

As is with the standard contract clauses cited at the beginning, if the contract does not identify the number of anticipated weather days or provide average units of weather in the contract documents, yet requires the contractor to consider the “norm” in its planned duration, the contractor will still need to account for the days in its project schedule and be able to properly measure and document weather-related delays as the project progresses.  In this case, it is advisable that the owner make sure it understands how the contractor has calculated the “norm” (in number of days), whether or not additional days beyond the actual weather occurrence were included, and how the contractor plans to evaluate the “norm” during the course of the project.  The key to successfully incorporating the “reasonably anticipated” weather days into the project schedule and effectively and efficiently evaluating time extensions hinges upon the parties’ full understanding of the process prior to submitting the preliminary baseline schedule and starting work on the project.

A good example of a contract provision that attempts to avoid all of the questions that may arise by simply telling the contractor to plan for the “norm” is shown in the provision set forth below, which comes from the State of Tennessee.   Page 1 and 2 of RPA January 2002 Std 01252 Weather Delays states:



A. If the basis exists for an extension of time in accordance with paragraph 8.3 of the Conditions, an extension of time on the basis of weather may be granted only for the number of Weather Delay Days in excess of the number of days listed as the Standard Baseline for that month.


A. The Owner has reviewed weather data available from the National Oceanic and Atmospheric Administration and determined a Standard Baseline of average climatic range for Some Location.

B. Standard Baseline is defined as the normal number of calendar days for each month during which construction activity exposed to weather conditions is expected to be prevented and suspended by cause of adverse weather. Suspension of construction activity for the number of days each month as listed in the Standard Baseline is included in the Work and is not eligible for extension of Contract Time.

C. Standard Baseline is as flows:

Standard Baseline


A. Adverse Weather is defined as the occurrence of one or more of the following conditions within a twenty-four (24) hour day that prevents construction activity exposed to weather conditions or access to the site:

  1. Precipitation (rain, snow, or ice) in excess of one-tenth inch (0.10”) liquid measure.
  2. Temperatures that do not rise above that required for the day’s construction activity, if such temperature requirement is specified or accepted as standard industry practice.
  3. Sustained wind in excess of twenty-five (25) m.p.h.

B. Adverse Weather may include, if appropriate, “dry-out” or “mud” days:

  1. resulting from precipitation days that occur beyond the standard baseline;
  2. only if there is a hindrance to site access or sitework and Contractor has taken all reasonable accommodations to avoid such hindrance; and,
  3. at a rate no greater than 1 make-up day for each day or consecutive days of precipitation beyond the standard baseline that total 1.0 inch or more, liquid measure, unless specifically recommended otherwise by the Designer.

C. A Weather Delay Day may be counted if adverse weather prevents work on the project for fifty percent (50%) or more of the contractor’s scheduled work day and critical path construction activities were included in the day’s schedule, including a weekend day or holiday if Contractor has scheduled construction activity that day.

D. Contractor shall take into account that certain construction activities are more affected by adverse weather and seasonal conditions than other activities, and that “dry-out” or “mud” days are not eligible to be counted as Weather Delay Day until the standard baseline is exceeded. Hence, Contractor should allow for an appropriate number of additional days associated with the Standard Baseline days in which such applicable construction activities are expected to be prevented and suspended.

The contract continued by stipulating the documentation and submittals that were necessary when requesting an extension to the contract time.  By providing the contractor with not only the actual number of “reasonably anticipated” weather days for each month of the year and where the information was obtained, the owner also has provided the definition of what an “Adverse Weather” day is and to what extent a workday’s critical activity must be delayed in order to receive a time extension.  The clause does leave some interpretation with regard to “dry-out” or “mud” days and does not directly address what happens to any unused weather days for any given month.  Although the clause is not perfect, it has certainly narrowed the margin with regard to the amount of interpretations that is required.

Next Month, John Crane will discuss weather and the project schedule.

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