Water and Atmospheric Resources Monitoring Program - , Illinois State Water Survey

Water and Atmospheric Resources Monitoring Program (WARM)

Weather Soil Groundwater Sediment Streamflow Reservoirs

Daily Pest Degree-Day Accumulations: Background

Daily weather data for this program are collected by the Water and Atmospheric Resources Monitoring (WARM) Program. Pest information is provided by the Integrated Pest Management (IPM) Program.

The IPM staff have provided information on base temperatures and degree-day accumulation thresholds, as they relate to development stages for specific pests. Weather data are obtained from a 19-station array of automated weather stations in Illinois, operated by WARM, called the Illinois Climate Network or ICN (Hollinger et al. 1994).

Pest degree-day totals are computed using the sine wave method of Allen (1976). One- and two-week projections are based on the past 11 years of climate data (Easterling et al., 1990) at each ICN site. All pest degree-day accumulations have a maximum temperature of 95° F, above which development of the organism does not progress.

Quality control of weather data is a high priority. However, degree-day data based on the most recent information must be considered as provisional because data are provided here early each day through a totally automated process. Sensor malfunctions at weather stations, as well as communication and power interruptions at the sites, do occur, which may influence downloaded data. These occurrences could result in spurious degree-day accumulations prior to quality control verification and data edits.


Allen, J. C., 1976. A modified sine wave method for calculating degree-days. Enviromental. Entomology 5(3), 388-396.

Easterling, W. E. , J. R. Angel, and S. A. Kirsh, 1990. The Appropriate Use of Climatic Information in Illinois Natural-Gas Utility Weather-Normalization Techniques. Illinois State Water Survey Report of Investigation 112, Champaign, Illinois, 31 pp.

Hollinger, S. E., Reinke, B. C., and Peppler, R. A., 1994. Illinois Climate Network: Site Descriptions, Instrumentation, and Data Management, Illinois State Water Survey Circular 178, Champaign, Illinois, 63 pp.

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