Northwest Degree Day Information

This page of basic Degree Day information has been developed in cooperation with Dr. Len Coop, Oregon State University - Oregon IPM Center. For those interested in more in depth information, Dr. Coop maintains a full feature IPM weather data and degree-day site. Access the Berries Northwest website.

The degree-day numbers in the table below represent the year-to-date accumulation calculated using 41 degrees as the base low temperature. To make a simplistic comparison, assume that approximately 10-20 heat units are gained per day during a typical spring/early summer day (west of the Cascades). For example: if the 2026 year-to-date number is 650 and the 2025 year-to-date number is 700, then you could figure that 2026 is about 3-5 days behind 2025.

For more detail you can Click on the station locations to see the station info and current weather data and/or Click on the degree-day numbers to run the calculator to 1) verify that the weather data is valid, 2) check the orange tortrix model which also uses a 41 degree threshold, 3) see the forecasted weather (if available), and 4) compare degree-day accumulations vs. the 30 year historical normals in a summary graph.

In presenting this information, we wish to stress that errors can occur. Use the information with caution. Predictive models do not replace the need for monitoring in the field. If you observe conditions that differ substantially from model predictions, please contact Dr. Coop to determine if the model inputs were incorrect, if the model functioning or weather data are in error, or if the model is inappropriate for your conditions. Dr. Coop's project was funded in part by grants from the NPDN, National Plant Diagnostics Network, the NRI Plant Biosecurity Program, and from prior grants from the USDA-Western Regional IPM program and from Oregon Statewide IPM funds.