Using DEOS Weather Data and Tools to Make Farm Decisions

Kevin Brinson, Associate State Climatologist and DEOS Director;

As any farmer knows, the weather can make you or break you. Weather forecasts are obviously helpful, but they’re usually pretty basic and limited to temperatures and precipitation over the next seven days. For some farm decisions, you need other types of information and data. A resource that offers some of this other information is the Delaware Environmental Observing System (DEOS) network. DEOS has been around since 2004 and collects and archives weather data for over 40 locations around Delaware. Each DEOS station collects temperature, relative humidity, winds, solar radiation, and precipitation data in real-time every 5 minutes. Some stations even collect top level (2-5 inches) soil moisture and soil temperature data. All of this information and data can be found on the DEOS website at

Beyond the usual weather data, DEOS also provides some additional information that is commonly used for farm decisions. The AgWeather summaries pages ( has a simple form for selecting a station and month to see a number of different daily weather values for the month you selected. The main ones of interest to farming applications are daily reference evapotranspiration, growing degree days (base 50 degrees F), and for some stations, daily volumetric water content and soil temperature. Each year, I get a number of inquiries about the soil temperature data, which some farmers use to determine when to plant crops or estimate how soon a weed or pest will emerge. The reference evaporation (RefET) data provides a measure of how much water is used by reference grass surface, which is a good proxy for crops. Long periods of high RefET (0.2 to 0.3 inches/day) with little or no precipitation can obviously take its toll on dryland crops. For irrigated farming, DEOS offers an irrigation scheduling system called DIMS ( DIMS offers a simple interface for users to enter and manage the crop water needs of an unlimited number of fields. Recently, we added a predictive capability to DIMS (see figure), where a user can try different amounts of irrigation out to five days in the future to determine which amount and day(s) would be optimal for providing sufficient water to a field’s crop. If you’re interested in using DIMS, users can sign up for a free account by e-mailing me at

DIMS prediction tool interface

The DIMS prediction tool interface.

DEOS network data are also used to drive a couple of crop disease models. The first is the Delaware Downy Mildew Lima Bean Risk Tool ( This tool uses a similar interface to DIMS, but provides a risk value for each field defined by a user based on the weather conditions, disease history of the field, and vulnerability of the cultivar planted. Also, like DIMS, access is free, but users must sign up for an account. The second crop disease model is operated by Penn State University for fusarium head blight (i.e., “wheat scab”), which is available at Users can select locations in Delaware to assess the risk of infection based on past and future environmental conditions and variety susceptibility information.

The DEOS network is part of the Center for Environmental Monitoring and Analysis at the University of Delaware, which also houses the Delaware State Climate Office ( If you have a need for historical weather and climate data (e.g., first/last frost dates, climate variable trends, etc.) please let us know.