Project execution is often delayed by extreme and unforeseen weather conditions. This is because extreme weather usually causes work disruption, waste of resources, significant project delays and, eventually, financial losses for both the contractor and the project owner. Construction contracts generally include weather-related clauses addressing when, and to what extent, the responsibilities and consequences of adverse weather are to be shared or compensated. However, setting clear and objective limits for abnormal weather is problematic, starting with the lack of agreement about which weather conditions can be considered as "normal" or "average”. Research on the influence of weather on construction productivity is scarce and underdeveloped. Therefore, practitioners cannot count on sound methods to mediate in and evaluate weather-related contract disputes. In these situations, claims are likely to arise and escalate. A stochastic model for objectively evaluating the weather influence during the execution stage is proposed. This model allows actual weather to be compared to historical data in a way that provides an objective assessment of the extent to which the adverse weather was (or not) exceptional. A case study of a fictional project is used to show its implementation. This is the first tool of its kind to address this concern with a straightforward, holistic and quantitative approach.
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