How to write the notice that the decoration company delayed the construction period due to the epidemic?

A construction company: During the construction of a building project, a large area of foundation pit collapsed due to a sudden rainstorm on a certain day of a month, which led to a serious delay in the progress of the project. As the rain is caused by your unforeseeable and irresistible bad weather, and it is not your responsibility, we agree to your application for extension of the construction period, and the extension of the construction period is determined to be 16 days.