By Scout Nelson
The ND Delta T forecast website is now available for the 2026 growing season and has expanded its coverage to include Minnesota. The online tool provides valuable weather information that can help agricultural applicators make better decisions when planning pesticide and herbicide applications.
Rob Proulx, Extension ag technology and grain systems specialist at North Dakota State University, highlighted that the expanded website provides both North Dakota and Minnesota users with important Delta T forecasts and historical weather information to support spray application management. The website can be accessed through https://ndawn.info by navigating to Agriculture, Ag Tools, and Delta-T Forecast.
Delta T measures the evaporative capacity of the air. Higher Delta T values indicate drier air and greater evaporation potential. When Delta T values rise above 14°F, spray droplets may evaporate too quickly, reducing herbicide effectiveness. These impacts are often more noticeable when using Fine or Medium spray qualities. Products containing glufosinate (Liberty) may be especially affected under elevated Delta T conditions.
The website provides several useful features for applicators across North Dakota and Minnesota. Users can view current Delta T maps generated through NDAWN and MAWN networks. The platform also offers forecast maps showing maximum Delta T values for the current day and the following five days.
In addition, the site includes historical Delta T maps dating back to late March and a table displaying hourly Delta T forecasts from 6 a.m. to 6 p.m. each day. These tools allow users to monitor weather conditions before and during spraying operations.
The website’s About page offers additional background information and explains how the tool can support field decisions. Applicators can use the forecasts to identify days when Delta T values may enter caution or unsuitable ranges and adjust spraying schedules accordingly. The site also encourages users to regularly monitor changing weather conditions and use historical data when investigating cases of reduced pesticide performance.
Following positive feedback from the 2025 version, the expanded 2026 platform now mirrors the coverage area of the Minnesota Ag Weather Network. Users wishing to provide feedback may contact Rob Proulx at rob.proulx@ndsu.edu.
Photo Credit: gettyimages-seregalsv
Categories: Minnesota, Weather