TETRA TECH INC

We experience seasonal trends in our business. Our revenue and operating income are typically lower in the first half of our fiscal year, primarily due to the Thanksgiving (in the U.S. and Canada), Christmas and New Year's holidays. Many of our clients' employees, as well as our own employees, take vacations during these holiday periods. Further, seasonal inclement weather conditions occasionally cause some of our offices to close temporarily or may hamper our project field work in the northern hemisphere's temperate and arctic regions. These occurrences result in fewer billable hours worked on projects and, correspondingly, less revenue recognized.