Part 4 of a 4 Part Series on Incorporating Weather Days into Your Project’s CPM Schedule

By Mark Nagata & Bill Haydt

This article was first published on Trauner Ideas & Insights and is republished here with permission. Copyright © 2018 Trauner Consulting Services, Inc. All rights reserved.

3. Insert an “Adverse Weather” Activity for All Anticipated Adverse Weather for the Project Duration

Instead of burying anticipated adverse weather days in the schedule work calendars or weather-sensitive activity durations, another option would be to add an “Anticipated Adverse Weather” activity at the end of the schedule, but before the project’s completion milestone, to represent all of the required anticipated adverse weather (see Figure 6, below).

As the project progresses, and adverse weather is encountered, the duration of this activity is reduced to account for the amount of adverse weather that was actually experienced on the project. This approach is a clean way to account for anticipated adverse weather without having to predict and select the workdays lost to adverse weather in the schedule’s work calendar or bury them in activity durations.

However, a significant criticism of this approach is that on multi-year projects where “all” of the anticipated adverse weather is included at the end of the schedule, the schedule would fail to reasonably forecast the early start and early finish dates for all of the work activities. For example, for the work in the second or third year, the work activities would be forecasted to begin much earlier than would reasonably be expected because the first year of the schedule would not include any anticipated workdays lost to weather. Depending on the project type, this issue may or may not be a problem.

Another criticism of this approach is that the added adverse weather activity would apply not only to the weather-sensitive work, but also to non-weather-sensitive work, as well. This approach may be better suited for projects with shorter durations.

When selecting a method to incorporate adverse weather into their project schedules, contractors should make their decision on a project-by-project basis. Taking into consideration their contractual requirements, the type of project being built, and the project’s location-specific weather conditions when they develop, their baseline schedule will help ensure that they select the best approach for demonstrating that they’ve properly accounted for anticipated adverse weather in their construction plan.

Bill Haydt and Mark Nagata are Director, Shareholders of TRAUNER. Their expertise lies in the areas of construction claims preparation and evaluation, development and review of critical path method (CPM) schedules, delay analysis, training, and dispute resolution. They direct and perform all types of analyses from schedule delay analyses to inefficiency analyses and the calculation of damages.

Bill can be reached at

Mark can be reached at

More in the next blog post about weather decision support, weather safety and weather risk management…

(Source: Nagata, Mark, and Bill Haydt. “Incorporating Weather Days into Your Project’s CPM Schedule.” Trauner Consulting Services,

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