The USA National Phenology Network generates daily growing degree day maps for the United States at fine spatial resolution (2.5–3.0 km) using a January 1 start date and two common base temperatures. Maps are available up to 6 days into the future and can be viewed and manipulated using an online visualization tool or downloaded as image or raster files. By exploring these maps through the visualization tool, it is possible to see how heat accumulation over the course of the year varies from average conditions and to anticipate when heat accumulation thresholds will be met.
Crimmins, T. M. (2018). Applying the USA National Phenology Network's Growing Degree Day Maps in Making Management Decisions. The Journal of Extension, 56(3), Article 2. https://tigerprints.clemson.edu/joe/vol56/iss3/2