Although adverse weather has impacted construction since before the pyramids, and when unusually severe is typically only deserving of a time extension without compensation, weather issues continue to generate their fair share of disputes. Even if not disputed, all significant grass root construction projects face weather impact issues that the parties may wish to recognize on an ongoing basis. Existing weather modeling methods can be cumbersome, overly technical, and resource intense. In searching for practical approaches, the authors have developed new methodologies for modeling force majeure weather that provide an objective evaluation of adverse weather impacts, for forensic as well as contemporaneous applications. Guidance for calculating normal adverse weather and force majeure weather day losses is provided, with examples to illustrate the new concepts. The focus of this paper is on the technical aspects of normal adverse weather and force majeure weather as opposed to the legal aspects.

Adverse Weather
Construction is impacted by adverse weather, with the actual impact varying from project to project, the site location and the region. The greatest impacts of adverse weather are upon construction exposed to the elements, whether directly as in the case of earthwork, concrete, etc. or when working inside the interior, non-conditioned spaces. Precipitation, high winds, cold and hot temperatures, high rates of snowfall, not to mention exceptional weather events (acts of God), can all adversely affect progress, the production rate of the workforce, and worker productivity.

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Dr. Gui Ponce de Leon, PE, PMP, LEED AP
Darrell D. Field, PE, LEED AP
John M. Zann, PE, LEED AP

Presented at PMI College of Scheduling Conference Meeting 2010

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